research questions examples about covid 19

Greater Good Science Center • Magazine • In Action • In Education

11 Questions to Ask About COVID-19 Research

Debates have raged on social media, around dinner tables, on TV, and in Congress about the science of COVID-19. Is it really worse than the flu? How necessary are lockdowns? Do masks work to prevent infection? What kinds of masks work best? Is the new vaccine safe?

You might see friends, relatives, and coworkers offer competing answers, often brandishing studies or citing individual doctors and scientists to support their positions. With so much disagreement—and with such high stakes—how can we use science to make the best decisions?

Here at Greater Good , we cover research into social and emotional well-being, and we try to help people apply findings to their personal and professional lives. We are well aware that our business is a tricky one.

Summarizing scientific studies and distilling the key insights that people can apply to their lives isn’t just difficult for the obvious reasons, like understanding and then explaining formal science terms or rigorous empirical and analytic methods to non-specialists. It’s also the case that context gets lost when we translate findings into stories, tips, and tools, especially when we push it all through the nuance-squashing machine of the Internet. Many people rarely read past the headlines, which intrinsically aim to be relatable and provoke interest in as many people as possible. Because our articles can never be as comprehensive as the original studies, they almost always omit some crucial caveats, such as limitations acknowledged by the researchers. To get those, you need access to the studies themselves.

And it’s very common for findings and scientists to seem to contradict each other. For example, there were many contradictory findings and recommendations about the use of masks, especially at the beginning of the pandemic—though as we’ll discuss, it’s important to understand that a scientific consensus did emerge.

Given the complexities and ambiguities of the scientific endeavor, is it possible for a non-scientist to strike a balance between wholesale dismissal and uncritical belief? Are there red flags to look for when you read about a study on a site like Greater Good or hear about one on a Fox News program? If you do read an original source study, how should you, as a non-scientist, gauge its credibility?

Here are 11 questions you might ask when you read about the latest scientific findings about the pandemic, based on our own work here at Greater Good.

1. Did the study appear in a peer-reviewed journal?

In peer review, submitted articles are sent to other experts for detailed critical input that often must be addressed in a revision prior to being accepted and published. This remains one of the best ways we have for ascertaining the rigor of the study and rationale for its conclusions. Many scientists describe peer review as a truly humbling crucible. If a study didn’t go through this process, for whatever reason, it should be taken with a much bigger grain of salt. 

“When thinking about the coronavirus studies, it is important to note that things were happening so fast that in the beginning people were releasing non-peer reviewed, observational studies,” says Dr. Leif Hass, a family medicine doctor and hospitalist at Sutter Health’s Alta Bates Summit Medical Center in Oakland, California. “This is what we typically do as hypothesis-generating but given the crisis, we started acting on them.”

In a confusing, time-pressed, fluid situation like the one COVID-19 presented, people without medical training have often been forced to simply defer to expertise in making individual and collective decisions, turning to culturally vetted institutions like the Centers for Disease Control (CDC). Is that wise? Read on.

2. Who conducted the study, and where did it appear?

“I try to listen to the opinion of people who are deep in the field being addressed and assess their response to the study at hand,” says Hass. “With the MRNA coronavirus vaccines, I heard Paul Offit from UPenn at a UCSF Grand Rounds talk about it. He literally wrote the book on vaccines. He reviewed what we know and gave the vaccine a big thumbs up. I was sold.”

From a scientific perspective, individual expertise and accomplishment matters—but so does institutional affiliation.

Why? Because institutions provide a framework for individual accountability as well as safety guidelines. At UC Berkeley, for example , research involving human subjects during COVID-19 must submit a Human Subjects Proposal Supplement Form , and follow a standard protocol and rigorous guidelines . Is this process perfect? No. It’s run by humans and humans are imperfect. However, the conclusions are far more reliable than opinions offered by someone’s favorite YouTuber .

Recommendations coming from institutions like the CDC should not be accepted uncritically. At the same time, however, all of us—including individuals sporting a “Ph.D.” or “M.D.” after their names—must be humble in the face of them. The CDC represents a formidable concentration of scientific talent and knowledge that dwarfs the perspective of any one individual. In a crisis like COVID-19, we need to defer to that expertise, at least conditionally.

“If we look at social media, things could look frightening,” says Hass. When hundreds of millions of people are vaccinated, millions of them will be afflicted anyway, in the course of life, by conditions like strokes, anaphylaxis, and Bell’s palsy. “We have to have faith that people collecting the data will let us know if we are seeing those things above the baseline rate.”

3. Who was studied, and where?

Animal experiments tell scientists a lot, but their applicability to our daily human lives will be limited. Similarly, if researchers only studied men, the conclusions might not be relevant to women, and vice versa.

Many psychology studies rely on WEIRD (Western, educated, industrialized, rich and democratic) participants, mainly college students, which creates an in-built bias in the discipline’s conclusions. Historically, biomedical studies also bias toward gathering measures from white male study participants, which again, limits generalizability of findings. Does that mean you should dismiss Western science? Of course not. It’s just the equivalent of a “Caution,” “Yield,” or “Roadwork Ahead” sign on the road to understanding.

This applies to the coronavirus vaccines now being distributed and administered around the world. The vaccines will have side effects; all medicines do. Those side effects will be worse for some people than others, depending on their genetic inheritance, medical status, age, upbringing, current living conditions, and other factors.

For Hass, it amounts to this question: Will those side effects be worse, on balance, than COVID-19, for most people?

“When I hear that four in 100,000 [of people in the vaccine trials] had Bell’s palsy, I know that it would have been a heck of a lot worse if 100,000 people had COVID. Three hundred people would have died and many others been stuck with chronic health problems.”

4. How big was the sample?

In general, the more participants in a study, the more valid its results. That said, a large sample is sometimes impossible or even undesirable for certain kinds of studies. During COVID-19, limited time has constrained the sample sizes.

However, that acknowledged, it’s still the case that some studies have been much larger than others—and the sample sizes of the vaccine trials can still provide us with enough information to make informed decisions. Doctors and nurses on the front lines of COVID-19—who are now the very first people being injected with the vaccine—think in terms of “biological plausibility,” as Hass says.

Did the admittedly rushed FDA approval of the Pfizer-BioNTech vaccine make sense, given what we already know? Tens of thousands of doctors who have been grappling with COVID-19 are voting with their arms, in effect volunteering to be a sample for their patients. If they didn’t think the vaccine was safe, you can bet they’d resist it. When the vaccine becomes available to ordinary people, we’ll know a lot more about its effects than we do today, thanks to health care providers paving the way.

5. Did the researchers control for key differences, and do those differences apply to you?

Diversity or gender balance aren’t necessarily virtues in experimental research, though ideally a study sample is as representative of the overall population as possible. However, many studies use intentionally homogenous groups, because this allows the researchers to limit the number of different factors that might affect the result.

While good researchers try to compare apples to apples, and control for as many differences as possible in their analyses, running a study always involves trade-offs between what can be accomplished as a function of study design, and how generalizable the findings can be.

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You also need to ask if the specific population studied even applies to you. For example, when one study found that cloth masks didn’t work in “high-risk situations,” it was sometimes used as evidence against mask mandates.

However, a look beyond the headlines revealed that the study was of health care workers treating COVID-19 patients, which is a vastly more dangerous situation than, say, going to the grocery store. Doctors who must intubate patients can end up being splattered with saliva. In that circumstance, one cloth mask won’t cut it. They also need an N95, a face shield, two layers of gloves, and two layers of gown. For the rest of us in ordinary life, masks do greatly reduce community spread, if as many people as possible are wearing them.

6. Was there a control group?

One of the first things to look for in methodology is whether the population tested was randomly selected, whether there was a control group, and whether people were randomly assigned to either group without knowing which one they were in. This is especially important if a study aims to suggest that a certain experience or treatment might actually cause a specific outcome, rather than just reporting a correlation between two variables (see next point).

For example, were some people randomly assigned a specific meditation practice while others engaged in a comparable activity or exercise? If the sample is large enough, randomized trials can produce solid conclusions. But, sometimes, a study will not have a control group because it’s ethically impossible. We can’t, for example, let sick people go untreated just to see what would happen. Biomedical research often makes use of standard “treatment as usual” or placebos in control groups. They also follow careful ethical guidelines to protect patients from both maltreatment and being deprived necessary treatment. When you’re reading about studies of masks, social distancing, and treatments during the COVID-19, you can partially gauge the reliability and validity of the study by first checking if it had a control group. If it didn’t, the findings should be taken as preliminary.

7. Did the researchers establish causality, correlation, dependence, or some other kind of relationship?

We often hear “Correlation is not causation” shouted as a kind of battle cry, to try to discredit a study. But correlation—the degree to which two or more measurements seem connected—is important, and can be a step toward eventually finding causation—that is, establishing a change in one variable directly triggers a change in another. Until then, however, there is no way to ascertain the direction of a correlational relationship (does A change B, or does B change A), or to eliminate the possibility that a third, unmeasured factor is behind the pattern of both variables without further analysis.

In the end, the important thing is to accurately identify the relationship. This has been crucial in understanding steps to counter the spread of COVID-19 like shelter-in-place orders. Just showing that greater compliance with shelter-in-place mandates was associated with lower hospitalization rates is not as conclusive as showing that one community that enacted shelter-in-place mandates had lower hospitalization rates than a different community of similar size and population density that elected not to do so.

We are not the first people to face an infection without understanding the relationships between factors that would lead to more of it. During the bubonic plague, cities would order rodents killed to control infection. They were onto something: Fleas that lived on rodents were indeed responsible. But then human cases would skyrocket.

Why? Because the fleas would migrate off the rodent corpses onto humans, which would worsen infection. Rodent control only reduces bubonic plague if it’s done proactively; once the outbreak starts, killing rats can actually make it worse. Similarly, we can’t jump to conclusions during the COVID-19 pandemic when we see correlations.

8. Are journalists and politicians, or even scientists, overstating the result?

Language that suggests a fact is “proven” by one study or which promotes one solution for all people is most likely overstating the case. Sweeping generalizations of any kind often indicate a lack of humility that should be a red flag to readers. A study may very well “suggest” a certain conclusion but it rarely, if ever, “proves” it.

This is why we use a lot of cautious, hedging language in Greater Good , like “might” or “implies.” This applies to COVID-19 as well. In fact, this understanding could save your life.

When President Trump touted the advantages of hydroxychloroquine as a way to prevent and treat COVID-19, he was dramatically overstating the results of one observational study. Later studies with control groups showed that it did not work—and, in fact, it didn’t work as a preventative for President Trump and others in the White House who contracted COVID-19. Most survived that outbreak, but hydroxychloroquine was not one of the treatments that saved their lives. This example demonstrates how misleading and even harmful overstated results can be, in a global pandemic.

9. Is there any conflict of interest suggested by the funding or the researchers’ affiliations?

A 2015 study found that you could drink lots of sugary beverages without fear of getting fat, as long as you exercised. The funder? Coca Cola, which eagerly promoted the results. This doesn’t mean the results are wrong. But it does suggest you should seek a second opinion : Has anyone else studied the effects of sugary drinks on obesity? What did they find?

It’s possible to take this insight too far. Conspiracy theorists have suggested that “Big Pharma” invented COVID-19 for the purpose of selling vaccines. Thus, we should not trust their own trials showing that the vaccine is safe and effective.

But, in addition to the fact that there is no compelling investigative evidence that pharmaceutical companies created the virus, we need to bear in mind that their trials didn’t unfold in a vacuum. Clinical trials were rigorously monitored and independently reviewed by third-party entities like the World Health Organization and government organizations around the world, like the FDA in the United States.

Does that completely eliminate any risk? Absolutely not. It does mean, however, that conflicts of interest are being very closely monitored by many, many expert eyes. This greatly reduces the probability and potential corruptive influence of conflicts of interest.

10. Do the authors reference preceding findings and original sources?

The scientific method is based on iterative progress, and grounded in coordinating discoveries over time. Researchers study what others have done and use prior findings to guide their own study approaches; every study builds on generations of precedent, and every scientist expects their own discoveries to be usurped by more sophisticated future work. In the study you are reading, do the researchers adequately describe and acknowledge earlier findings, or other key contributions from other fields or disciplines that inform aspects of the research, or the way that they interpret their results?

Greater Good’s Guide to Well-Being During Coronavirus

Practices, resources, and articles for individuals, parents, and educators facing COVID-19

This was crucial for the debates that have raged around mask mandates and social distancing. We already knew quite a bit about the efficacy of both in preventing infections, informed by centuries of practical experience and research.

When COVID-19 hit American shores, researchers and doctors did not question the necessity of masks in clinical settings. Here’s what we didn’t know: What kinds of masks would work best for the general public, who should wear them, when should we wear them, were there enough masks to go around, and could we get enough people to adopt best mask practices to make a difference in the specific context of COVID-19 ?

Over time, after a period of confusion and contradictory evidence, those questions have been answered . The very few studies that have suggested masks don’t work in stopping COVID-19 have almost all failed to account for other work on preventing the disease, and had results that simply didn’t hold up. Some were even retracted .

So, when someone shares a coronavirus study with you, it’s important to check the date. The implications of studies published early in the pandemic might be more limited and less conclusive than those published later, because the later studies could lean on and learn from previously published work. Which leads us to the next question you should ask in hearing about coronavirus research…

11. Do researchers, journalists, and politicians acknowledge limitations and entertain alternative explanations?

Is the study focused on only one side of the story or one interpretation of the data? Has it failed to consider or refute alternative explanations? Do they demonstrate awareness of which questions are answered and which aren’t by their methods? Do the journalists and politicians communicating the study know and understand these limitations?

When the Annals of Internal Medicine published a Danish study last month on the efficacy of cloth masks, some suggested that it showed masks “make no difference” against COVID-19.

The study was a good one by the standards spelled out in this article. The researchers and the journal were both credible, the study was randomized and controlled, and the sample size (4,862 people) was fairly large. Even better, the scientists went out of their way to acknowledge the limits of their work: “Inconclusive results, missing data, variable adherence, patient-reported findings on home tests, no blinding, and no assessment of whether masks could decrease disease transmission from mask wearers to others.”

Unfortunately, their scientific integrity was not reflected in the ways the study was used by some journalists, politicians, and people on social media. The study did not show that masks were useless. What it did show—and what it was designed to find out—was how much protection masks offered to the wearer under the conditions at the time in Denmark. In fact, the amount of protection for the wearer was not large, but that’s not the whole picture: We don’t wear masks mainly to protect ourselves, but to protect others from infection. Public-health recommendations have stressed that everyone needs to wear a mask to slow the spread of infection.

“We get vaccinated for the greater good, not just to protect ourselves ”

As the authors write in the paper, we need to look to other research to understand the context for their narrow results. In an editorial accompanying the paper in Annals of Internal Medicine , the editors argue that the results, together with existing data in support of masks, “should motivate widespread mask wearing to protect our communities and thereby ourselves.”

Something similar can be said of the new vaccine. “We get vaccinated for the greater good, not just to protect ourselves,” says Hass. “Being vaccinated prevents other people from getting sick. We get vaccinated for the more vulnerable in our community in addition for ourselves.”

Ultimately, the approach we should take to all new studies is a curious but skeptical one. We should take it all seriously and we should take it all with a grain of salt. You can judge a study against your experience, but you need to remember that your experience creates bias. You should try to cultivate humility, doubt, and patience. You might not always succeed; when you fail, try to admit fault and forgive yourself.

Above all, we need to try to remember that science is a process, and that conclusions always raise more questions for us to answer. That doesn’t mean we never have answers; we do. As the pandemic rages and the scientific process unfolds, we as individuals need to make the best decisions we can, with the information we have.

This article was revised and updated from a piece published by Greater Good in 2015, “ 10 Questions to Ask About Scientific Studies .”

About the Authors

Jeremy Adam Smith

Uc berkeley.

Jeremy Adam Smith edits the GGSC’s online magazine, Greater Good . He is also the author or coeditor of five books, including The Daddy Shift , Are We Born Racist? , and (most recently) The Gratitude Project: How the Science of Thankfulness Can Rewire Our Brains for Resilience, Optimism, and the Greater Good . Before joining the GGSC, Jeremy was a John S. Knight Journalism Fellow at Stanford University.

Emiliana R. Simon-Thomas

Emiliana R. Simon-Thomas, Ph.D. , is the science director of the Greater Good Science Center, where she directs the GGSC’s research fellowship program and serves as a co-instructor of its Science of Happiness and Science of Happiness at Work online courses.

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The Impact of COVID-19 on the Careers of Women in Academic Sciences, Engineering, and Medicine (2021)

Chapter: 8 major findings and research questions, 8 major findings and research questions, introduction.

The COVID-19 pandemic, which began in late 2019, created unprecedented global disruption and infused a significant level of uncertainty into the lives of individuals, both personally and professionally, around the world throughout 2020. The significant effect on vulnerable populations, such as essential workers and the elderly, is well documented, as is the devastating effect the COVID-19 pandemic had on the economy, particularly brick-and-mortar retail and hospitality and food services. Concurrently, the deaths of unarmed Black people at the hands of law enforcement officers created a heightened awareness of the persistence of structural injustices in U.S. society.

Against the backdrop of this public health crisis, economic upheaval, and amplified social consciousness, an ad hoc committee was appointed to review the potential effects of the COVID-19 pandemic on women in academic science, technology, engineering, mathematics, and medicine (STEMM) during 2020. The committee’s work built on the National Academies of Sciences, Engineering, and Medicine report Promising Practices for Addressing the Underrepresentation of Women in Science, Engineering, and Medicine: Opening Doors (the Promising Practices report), which presents evidence-based recommendations to address the well-established structural barriers that impede the advancement of women in STEMM. However, the committee recognized that none of the actions identified in the Promising Practices report were conceived within the context of a pandemic, an economic downturn, or the emergence of national protests against structural racism. The representation and vitality of academic women in STEMM had already warranted national attention prior to these events, and the COVID-19

pandemic appeared to represent an additional risk to the fragile progress that women had made in some STEMM disciplines. Furthermore, the future will almost certainly hold additional, unforeseen disruptions, which underscores the importance of the committee’s work.

In times of stress, there is a risk that the divide will deepen between those who already have advantages and those who do not. In academia, senior and tenured academics are more likely to have an established reputation, a stable salary commitment, and power within the academic system. They are more likely, before the COVID-19 pandemic began, to have established professional networks, generated data that can be used to write papers, and achieved financial and job security. While those who have these advantages may benefit from a level of stability relative to others during stressful times, those who were previously systemically disadvantaged are more likely to experience additional strain and instability.

As this report has documented, during 2020 the COVID-19 pandemic had overall negative effects on women in academic STEMM in areas such productivity, boundary setting and boundary control, networking and community building, burnout rates, and mental well-being. The excessive expectations of caregiving that often fall on the shoulders of women cut across career timeline and rank (e.g., graduate student, postdoctoral scholar, non-tenure-track and other contingent faculty, tenure-track faculty), institution type, and scientific discipline. Although there have been opportunities for innovation and some potential shifts in expectations, increased caregiving demands associated with the COVID-19 pandemic in 2020, such as remote working, school closures, and childcare and eldercare, had disproportionately negative outcomes for women.

The effects of the COVID-19 pandemic on women in STEMM during 2020 are understood better through an intentionally intersectional lens. Productivity, career, boundary setting, mental well-being, and health are all influenced by the ways in which social identities are defined and cultivated within social and power structures. Race and ethnicity, sexual orientation, gender identity, academic career stage, appointment type, institution type, age, and disability status, among many other factors, can amplify or diminish the effects of the COVID-19 pandemic for a given person. For example, non-cisgender women may be forced to return to home environments where their gender identity is not accepted, increasing their stress and isolation, and decreasing their well-being. Women of Color had a higher likelihood of facing a COVID-19–related death in their family compared with their white, non-Hispanic colleagues. The full extent of the effects of the COVID-19 pandemic for women of various social identities was not fully understood at the end of 2020.

Considering the relative paucity of women in many STEMM fields prior to the COVID-19 pandemic, women are more likely to experience academic isolation, including limited access to mentors, sponsors, and role models that share gender, racial, or ethnic identities. Combining this reality with the physical isolation stipulated by public health responses to the COVID-19 pandemic,

women in STEMM were subject to increasing isolation within their fields, networks, and communities. Explicit attention to the early indicators of how the COVID-19 pandemic affected women in academic STEMM careers during 2020, as well as attention to crisis responses throughout history, may provide opportunities to mitigate some of the long-term effects and potentially develop a more resilient and equitable academic STEMM system.

MAJOR FINDINGS

Given the ongoing nature of the COVID-19 pandemic, it was not possible to fully understand the entirety of the short- or long-term implications of this global disruption on the careers of women in academic STEMM. Having gathered preliminary data and evidence available in 2020, the committee found that significant changes to women’s work-life boundaries and divisions of labor, careers, productivity, advancement, mentoring and networking relationships, and mental health and well-being have been observed. The following findings represent those aspects that the committee agreed have been substantiated by the preliminary data, evidence, and information gathered by the end of 2020. They are presented either as Established Research and Experiences from Previous Events or Impacts of the COVID-19 Pandemic during 2020 that parallel the topics as presented in the report.

Established Research and Experiences from Previous Events

___________________

1 This finding is primarily based on research on cisgender women and men.

Impacts of the COVID-19 Pandemic during 2020

Research questions.

While this report compiled much of the research, data, and evidence available in 2020 on the effects of the COVID-19 pandemic, future research is still needed to understand all the potential effects, especially any long-term implications. The research questions represent areas the committee identified for future research, rather than specific recommendations. They are presented in six categories that parallel the chapters of the report: Cross-Cutting Themes; Academic Productivity and Institutional Responses; Work-Life Boundaries and Gendered Divisions of Labor; Collaboration, Networking, and Professional Societies; Academic Leadership and Decision-Making; and Mental Health and Well-being. The committee hopes the report will be used as a basis for continued understanding of the impact of the COVID-19 pandemic in its entirety and as a reference for mitigating impacts of future disruptions that affect women in academic STEMM. The committee also hopes that these research questions may enable academic STEMM to emerge from the pandemic era a stronger, more equitable place for women. Therefore, the committee identifies two types of research questions in each category; listed first are those questions aimed at understanding the impacts of the disruptions from the COVID-19 pandemic, followed by those questions exploring the opportunities to help support the full participation of women in the future.

Cross-Cutting Themes

• What are the short- and long-term effects of the COVID-19 pandemic on the career trajectories, job stability, and leadership roles of women, particularly of Black women and other Women of Color? How do these effects vary across institutional characteristics, 2 discipline, and career stage?

2 Institutional characteristics include different institutional types (e.g., research university, liberal arts college, community college), locales (e.g., urban, rural), missions (e.g., Historically Black Colleges and Universities, Hispanic-Serving Institutions, Asian American/Native American/Pacific Islander-Serving Institutions, Tribal Colleges and Universities), and levels of resources.

• How did the confluence of structural racism, economic hardships, and environmental disruptions affect Women of Color during the COVID-19 pandemic? Specifically, how did the murder of George Floyd, Breonna Taylor, and other Black citizens impact Black women academics’ safety, ability to be productive, and mental health?
• How has the inclusion of women in leadership and other roles in the academy influenced the ability of institutions to respond to the confluence of major social crises during the COVID-19 pandemic?
• How can institutions build on the involvement women had across STEMM disciplines during the COVID-19 pandemic to increase the participation of women in STEMM and/or elevate and support women in their current STEMM-related positions?
• How can institutions adapt, leverage, and learn from approaches developed during 2020 to attend to challenges experienced by Women of Color in STEMM in the future?

Academic Productivity and Institutional Responses

• How did the institutional responses (e.g., policies, practices) that were outlined in the Major Findings impact women faculty across institutional characteristics and disciplines?
• What are the short- and long-term effects of faculty evaluation practices and extension policies implemented during the COVID-19 pandemic on the productivity and career trajectories of members of the academic STEMM workforce by gender?
• What adaptations did women use during the transition to online and hybrid teaching modes? How did these techniques and adaptations vary as a function of career stage and institutional characteristics?
• What are examples of institutional changes implemented in response to the COVID-19 pandemic that have the potential to reduce systemic barriers to participation and advancement that have historically been faced by academic women in STEMM, specifically Women of Color and other marginalized women in STEMM? How might positive institutional responses be leveraged to create a more resilient and responsive higher education ecosystem?
• How can or should funding arrangements be altered (e.g., changes in funding for research and/or mentorship programs) to support new ways of interaction for women in STEMM during times of disruption, such as the COVID-19 pandemic?

Work-Life Boundaries and Gendered Divisions of Labor

• How do different social identities (e.g., racial; socioeconomic status; culturally, ethnically, sexually, or gender diverse; immigration status; parents of young children and other caregivers; women without partners) influence the management of work-nonwork boundaries? How did this change during the COVID-19 pandemic?
• How have COVID-19 pandemic-related disruptions affected progress toward reducing the gender gap in academic STEMM labor-force participation? How does this differ for Women of Color or women with caregiving responsibilities?
• How can institutions account for the unique challenges of women faculty with parenthood and caregiving responsibilities when developing effective and equitable policies, practices, or programs?
• How might insights gained about work-life boundaries during the COVID-19 pandemic inform how institutions develop and implement supportive resources (e.g., reductions in workload, on-site childcare, flexible working options)?

Collaboration, Networking, and Professional Societies

• What were the short- and long-term effects of the COVID-19 pandemic-prompted switch from in-person conferences to virtual conferences on conference culture and climate, especially for women in STEMM?
• How will the increase in virtual conferences specifically affect women’s advancement and career trajectories? How will it affect women’s collaborations?
• How has the shift away from attending conferences and in-person networking changed longer-term mentoring and sponsoring relationships, particularly in terms of gender dynamics?
• How can institutions maximize the benefits of digitization and the increased use of technology observed during the COVID-19 pandemic to continue supporting women, especially marginalized women, by increasing accessibility, collaborations, mentorship, and learning?
• How can organizations that support, host, or facilitate online and virtual conferences and networking events (1) ensure open and fair access to participants who face different funding and time constraints; (2) foster virtual connections among peers, mentors, and sponsors; and (3) maintain an inclusive environment to scientists of all backgrounds?
• What policies, practices, or programs can be developed to help women in STEMM maintain a sense of support, structure, and stability during and after periods of disruption?

Academic Leadership and Decision-Making

• What specific interventions did colleges and universities initiate or prioritize to ensure that women were included in decision-making processes during responses to the COVID-19 pandemic?
• How effective were colleges and universities that prioritized equity-minded leadership, shared leadership, and crisis leadership styles at mitigating emerging and potential negative effects of the COVID-19 pandemic on women in their communities?
• What specific aspects of different leadership models translated to more effective strategies to advance women in STEMM, particularly during the COVID-19 pandemic?
• How can examples of intentional inclusion of women in decision-making processes during the COVID-19 pandemic be leveraged to develop the engagement of women as leaders at all levels of academic institutions?
• What are potential “top-down” structural changes in academia that can be implemented to mitigate the adverse effects of the COVID-19 pandemic or other disruptions?
• How can academic leadership, at all levels, more effectively support the mental health needs of women in STEMM?

Mental Health and Well-being

• What is the impact of the COVID-19 pandemic and institutional responses on the mental health and well-being of members of the academic STEMM workforce as a function of gender, race, and career stage?
• How are tools and diagnostic tests to measure aspects of wellbeing, including burnout and insomnia, used in academic settings? How does this change during times of increased stress, such as the COVID-19 pandemic?
• How might insights gained about mental health during the COVID-19 pandemic be used to inform preparedness for future disruptions?
• How can programs that focus on changes in biomarkers of stress and mood dysregulation, such as levels of sleep, activity, and texting patterns, be developed and implemented to better engage women in addressing their mental health?
• What are effective interventions to address the health of women academics in STEMM that specifically account for the effects of stress on women? What are effective interventions to mitigate the excessive levels of stress for Women of Color?

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The spring of 2020 marked a change in how almost everyone conducted their personal and professional lives, both within science, technology, engineering, mathematics, and medicine (STEMM) and beyond. The COVID-19 pandemic disrupted global scientific conferences and individual laboratories and required people to find space in their homes from which to work. It blurred the boundaries between work and non-work, infusing ambiguity into everyday activities. While adaptations that allowed people to connect became more common, the evidence available at the end of 2020 suggests that the disruptions caused by the COVID-19 pandemic endangered the engagement, experience, and retention of women in academic STEMM, and may roll back some of the achievement gains made by women in the academy to date.

The Impact of COVID-19 on the Careers of Women in Academic Sciences, Engineering, and Medicine identifies, names, and documents how the COVID-19 pandemic disrupted the careers of women in academic STEMM during the initial 9-month period since March 2020 and considers how these disruptions - both positive and negative - might shape future progress for women. This publication builds on the 2020 report Promising Practices for Addressing the Underrepresentation of Women in Science, Engineering, and Medicine to develop a comprehensive understanding of the nuanced ways these disruptions have manifested. The Impact of COVID-19 on the Careers of Women in Academic Sciences, Engineering, and Medicine will inform the academic community as it emerges from the pandemic to mitigate any long-term negative consequences for the continued advancement of women in the academic STEMM workforce and build on the adaptations and opportunities that have emerged.

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SARS-CoV-2 and COVID-19: revisiting the most important research questions

Affiliations.

• 1 School of Biomedical Sciences, The University of Hong Kong, 3/F Laboratory Block, 21 Sassoon Road, Pokfulam, Hong Kong.
• 2 School of Medical and Health Sciences, Tung Wah College, Kowloon, Hong Kong.
• 3 Department of Microbiology, The University of Hong Kong, Pokfulam, Hong Kong.
• 4 School of Biomedical Sciences, The University of Hong Kong, 3/F Laboratory Block, 21 Sassoon Road, Pokfulam, Hong Kong. [email protected].
• PMID: 34922626
• PMCID: PMC8683810
• DOI: 10.1186/s13578-021-00730-1

In February 2020, we highlighted the top nine important research questions on SARS-CoV-2 and COVID-19 concerning virus transmission, asymptomatic and presymptomatic virus shedding, diagnosis, treatment, vaccine development, origin of virus and viral pathogenesis. These and related questions are revisited at the end of 2021 to shed light on the roadmap of bringing an end to the pandemic.

Keywords: Antivirals; COVID-19; Endemic; Pandemic; SARS-CoV-2; Vaccines.

© 2021. The Author(s).

Grants and funding

• C7142-20GF/Research Grants Council, University Grants Committee
• T11-709/21-N/Research Grants Council, University Grants Committee
• COVID190114/Health and Medical Research Fund

• Research article
• Open access
• Published: 04 June 2021

Coronavirus disease (COVID-19) pandemic: an overview of systematic reviews

• Israel Júnior Borges do Nascimento 1 , 2 ,
• Dónal P. O’Mathúna 3 , 4 ,
• Thilo Caspar von Groote 5 ,
• Hebatullah Mohamed Abdulazeem 6 ,
• Ishanka Weerasekara 7 , 8 ,
• Ana Marusic 9 ,
• Livia Puljak   ORCID: orcid.org/0000-0002-8467-6061 10 ,
• Vinicius Tassoni Civile 11 ,
• Irena Zakarija-Grkovic 9 ,
• Tina Poklepovic Pericic 9 ,
• Alvaro Nagib Atallah 11 ,
• Santino Filoso 12 ,
• Nicola Luigi Bragazzi 13 &
• Milena Soriano Marcolino 1

On behalf of the International Network of Coronavirus Disease 2019 (InterNetCOVID-19)

BMC Infectious Diseases volume  21 , Article number:  525 ( 2021 ) Cite this article

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Navigating the rapidly growing body of scientific literature on the SARS-CoV-2 pandemic is challenging, and ongoing critical appraisal of this output is essential. We aimed to summarize and critically appraise systematic reviews of coronavirus disease (COVID-19) in humans that were available at the beginning of the pandemic.

Nine databases (Medline, EMBASE, Cochrane Library, CINAHL, Web of Sciences, PDQ-Evidence, WHO’s Global Research, LILACS, and Epistemonikos) were searched from December 1, 2019, to March 24, 2020. Systematic reviews analyzing primary studies of COVID-19 were included. Two authors independently undertook screening, selection, extraction (data on clinical symptoms, prevalence, pharmacological and non-pharmacological interventions, diagnostic test assessment, laboratory, and radiological findings), and quality assessment (AMSTAR 2). A meta-analysis was performed of the prevalence of clinical outcomes.

Eighteen systematic reviews were included; one was empty (did not identify any relevant study). Using AMSTAR 2, confidence in the results of all 18 reviews was rated as “critically low”. Identified symptoms of COVID-19 were (range values of point estimates): fever (82–95%), cough with or without sputum (58–72%), dyspnea (26–59%), myalgia or muscle fatigue (29–51%), sore throat (10–13%), headache (8–12%) and gastrointestinal complaints (5–9%). Severe symptoms were more common in men. Elevated C-reactive protein and lactate dehydrogenase, and slightly elevated aspartate and alanine aminotransferase, were commonly described. Thrombocytopenia and elevated levels of procalcitonin and cardiac troponin I were associated with severe disease. A frequent finding on chest imaging was uni- or bilateral multilobar ground-glass opacity. A single review investigated the impact of medication (chloroquine) but found no verifiable clinical data. All-cause mortality ranged from 0.3 to 13.9%.

Conclusions

In this overview of systematic reviews, we analyzed evidence from the first 18 systematic reviews that were published after the emergence of COVID-19. However, confidence in the results of all reviews was “critically low”. Thus, systematic reviews that were published early on in the pandemic were of questionable usefulness. Even during public health emergencies, studies and systematic reviews should adhere to established methodological standards.

Peer Review reports

The spread of the “Severe Acute Respiratory Coronavirus 2” (SARS-CoV-2), the causal agent of COVID-19, was characterized as a pandemic by the World Health Organization (WHO) in March 2020 and has triggered an international public health emergency [ 1 ]. The numbers of confirmed cases and deaths due to COVID-19 are rapidly escalating, counting in millions [ 2 ], causing massive economic strain, and escalating healthcare and public health expenses [ 3 , 4 ].

The research community has responded by publishing an impressive number of scientific reports related to COVID-19. The world was alerted to the new disease at the beginning of 2020 [ 1 ], and by mid-March 2020, more than 2000 articles had been published on COVID-19 in scholarly journals, with 25% of them containing original data [ 5 ]. The living map of COVID-19 evidence, curated by the Evidence for Policy and Practice Information and Co-ordinating Centre (EPPI-Centre), contained more than 40,000 records by February 2021 [ 6 ]. More than 100,000 records on PubMed were labeled as “SARS-CoV-2 literature, sequence, and clinical content” by February 2021 [ 7 ].

Due to publication speed, the research community has voiced concerns regarding the quality and reproducibility of evidence produced during the COVID-19 pandemic, warning of the potential damaging approach of “publish first, retract later” [ 8 ]. It appears that these concerns are not unfounded, as it has been reported that COVID-19 articles were overrepresented in the pool of retracted articles in 2020 [ 9 ]. These concerns about inadequate evidence are of major importance because they can lead to poor clinical practice and inappropriate policies [ 10 ].

Systematic reviews are a cornerstone of today’s evidence-informed decision-making. By synthesizing all relevant evidence regarding a particular topic, systematic reviews reflect the current scientific knowledge. Systematic reviews are considered to be at the highest level in the hierarchy of evidence and should be used to make informed decisions. However, with high numbers of systematic reviews of different scope and methodological quality being published, overviews of multiple systematic reviews that assess their methodological quality are essential [ 11 , 12 , 13 ]. An overview of systematic reviews helps identify and organize the literature and highlights areas of priority in decision-making.

In this overview of systematic reviews, we aimed to summarize and critically appraise systematic reviews of coronavirus disease (COVID-19) in humans that were available at the beginning of the pandemic.

Methodology

Research question.

This overview’s primary objective was to summarize and critically appraise systematic reviews that assessed any type of primary clinical data from patients infected with SARS-CoV-2. Our research question was purposefully broad because we wanted to analyze as many systematic reviews as possible that were available early following the COVID-19 outbreak.

Study design

We conducted an overview of systematic reviews. The idea for this overview originated in a protocol for a systematic review submitted to PROSPERO (CRD42020170623), which indicated a plan to conduct an overview.

Overviews of systematic reviews use explicit and systematic methods for searching and identifying multiple systematic reviews addressing related research questions in the same field to extract and analyze evidence across important outcomes. Overviews of systematic reviews are in principle similar to systematic reviews of interventions, but the unit of analysis is a systematic review [ 14 , 15 , 16 ].

We used the overview methodology instead of other evidence synthesis methods to allow us to collate and appraise multiple systematic reviews on this topic, and to extract and analyze their results across relevant topics [ 17 ]. The overview and meta-analysis of systematic reviews allowed us to investigate the methodological quality of included studies, summarize results, and identify specific areas of available or limited evidence, thereby strengthening the current understanding of this novel disease and guiding future research [ 13 ].

A reporting guideline for overviews of reviews is currently under development, i.e., Preferred Reporting Items for Overviews of Reviews (PRIOR) [ 18 ]. As the PRIOR checklist is still not published, this study was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2009 statement [ 19 ]. The methodology used in this review was adapted from the Cochrane Handbook for Systematic Reviews of Interventions and also followed established methodological considerations for analyzing existing systematic reviews [ 14 ].

Approval of a research ethics committee was not necessary as the study analyzed only publicly available articles.

Eligibility criteria

Systematic reviews were included if they analyzed primary data from patients infected with SARS-CoV-2 as confirmed by RT-PCR or another pre-specified diagnostic technique. Eligible reviews covered all topics related to COVID-19 including, but not limited to, those that reported clinical symptoms, diagnostic methods, therapeutic interventions, laboratory findings, or radiological results. Both full manuscripts and abbreviated versions, such as letters, were eligible.

No restrictions were imposed on the design of the primary studies included within the systematic reviews, the last search date, whether the review included meta-analyses or language. Reviews related to SARS-CoV-2 and other coronaviruses were eligible, but from those reviews, we analyzed only data related to SARS-CoV-2.

No consensus definition exists for a systematic review [ 20 ], and debates continue about the defining characteristics of a systematic review [ 21 ]. Cochrane’s guidance for overviews of reviews recommends setting pre-established criteria for making decisions around inclusion [ 14 ]. That is supported by a recent scoping review about guidance for overviews of systematic reviews [ 22 ].

Thus, for this study, we defined a systematic review as a research report which searched for primary research studies on a specific topic using an explicit search strategy, had a detailed description of the methods with explicit inclusion criteria provided, and provided a summary of the included studies either in narrative or quantitative format (such as a meta-analysis). Cochrane and non-Cochrane systematic reviews were considered eligible for inclusion, with or without meta-analysis, and regardless of the study design, language restriction and methodology of the included primary studies. To be eligible for inclusion, reviews had to be clearly analyzing data related to SARS-CoV-2 (associated or not with other viruses). We excluded narrative reviews without those characteristics as these are less likely to be replicable and are more prone to bias.

Scoping reviews and rapid reviews were eligible for inclusion in this overview if they met our pre-defined inclusion criteria noted above. We included reviews that addressed SARS-CoV-2 and other coronaviruses if they reported separate data regarding SARS-CoV-2.

Information sources

Nine databases were searched for eligible records published between December 1, 2019, and March 24, 2020: Cochrane Database of Systematic Reviews via Cochrane Library, PubMed, EMBASE, CINAHL (Cumulative Index to Nursing and Allied Health Literature), Web of Sciences, LILACS (Latin American and Caribbean Health Sciences Literature), PDQ-Evidence, WHO’s Global Research on Coronavirus Disease (COVID-19), and Epistemonikos.

The comprehensive search strategy for each database is provided in Additional file 1 and was designed and conducted in collaboration with an information specialist. All retrieved records were primarily processed in EndNote, where duplicates were removed, and records were then imported into the Covidence platform [ 23 ]. In addition to database searches, we screened reference lists of reviews included after screening records retrieved via databases.

Study selection

All searches, screening of titles and abstracts, and record selection, were performed independently by two investigators using the Covidence platform [ 23 ]. Articles deemed potentially eligible were retrieved for full-text screening carried out independently by two investigators. Discrepancies at all stages were resolved by consensus. During the screening, records published in languages other than English were translated by a native/fluent speaker.

Data collection process

We custom designed a data extraction table for this study, which was piloted by two authors independently. Data extraction was performed independently by two authors. Conflicts were resolved by consensus or by consulting a third researcher.

We extracted the following data: article identification data (authors’ name and journal of publication), search period, number of databases searched, population or settings considered, main results and outcomes observed, and number of participants. From Web of Science (Clarivate Analytics, Philadelphia, PA, USA), we extracted journal rank (quartile) and Journal Impact Factor (JIF).

We categorized the following as primary outcomes: all-cause mortality, need for and length of mechanical ventilation, length of hospitalization (in days), admission to intensive care unit (yes/no), and length of stay in the intensive care unit.

The following outcomes were categorized as exploratory: diagnostic methods used for detection of the virus, male to female ratio, clinical symptoms, pharmacological and non-pharmacological interventions, laboratory findings (full blood count, liver enzymes, C-reactive protein, d-dimer, albumin, lipid profile, serum electrolytes, blood vitamin levels, glucose levels, and any other important biomarkers), and radiological findings (using radiography, computed tomography, magnetic resonance imaging or ultrasound).

We also collected data on reporting guidelines and requirements for the publication of systematic reviews and meta-analyses from journal websites where included reviews were published.

Quality assessment in individual reviews

Two researchers independently assessed the reviews’ quality using the “A MeaSurement Tool to Assess Systematic Reviews 2 (AMSTAR 2)”. We acknowledge that the AMSTAR 2 was created as “a critical appraisal tool for systematic reviews that include randomized or non-randomized studies of healthcare interventions, or both” [ 24 ]. However, since AMSTAR 2 was designed for systematic reviews of intervention trials, and we included additional types of systematic reviews, we adjusted some AMSTAR 2 ratings and reported these in Additional file 2 .

Adherence to each item was rated as follows: yes, partial yes, no, or not applicable (such as when a meta-analysis was not conducted). The overall confidence in the results of the review is rated as “critically low”, “low”, “moderate” or “high”, according to the AMSTAR 2 guidance based on seven critical domains, which are items 2, 4, 7, 9, 11, 13, 15 as defined by AMSTAR 2 authors [ 24 ]. We reported our adherence ratings for transparency of our decision with accompanying explanations, for each item, in each included review.

One of the included systematic reviews was conducted by some members of this author team [ 25 ]. This review was initially assessed independently by two authors who were not co-authors of that review to prevent the risk of bias in assessing this study.

Synthesis of results

For data synthesis, we prepared a table summarizing each systematic review. Graphs illustrating the mortality rate and clinical symptoms were created. We then prepared a narrative summary of the methods, findings, study strengths, and limitations.

For analysis of the prevalence of clinical outcomes, we extracted data on the number of events and the total number of patients to perform proportional meta-analysis using RStudio© software, with the “meta” package (version 4.9–6), using the “metaprop” function for reviews that did not perform a meta-analysis, excluding case studies because of the absence of variance. For reviews that did not perform a meta-analysis, we presented pooled results of proportions with their respective confidence intervals (95%) by the inverse variance method with a random-effects model, using the DerSimonian-Laird estimator for τ 2 . We adjusted data using Freeman-Tukey double arcosen transformation. Confidence intervals were calculated using the Clopper-Pearson method for individual studies. We created forest plots using the RStudio© software, with the “metafor” package (version 2.1–0) and “forest” function.

Managing overlapping systematic reviews

Some of the included systematic reviews that address the same or similar research questions may include the same primary studies in overviews. Including such overlapping reviews may introduce bias when outcome data from the same primary study are included in the analyses of an overview multiple times. Thus, in summaries of evidence, multiple-counting of the same outcome data will give data from some primary studies too much influence [ 14 ]. In this overview, we did not exclude overlapping systematic reviews because, according to Cochrane’s guidance, it may be appropriate to include all relevant reviews’ results if the purpose of the overview is to present and describe the current body of evidence on a topic [ 14 ]. To avoid any bias in summary estimates associated with overlapping reviews, we generated forest plots showing data from individual systematic reviews, but the results were not pooled because some primary studies were included in multiple reviews.

Our search retrieved 1063 publications, of which 175 were duplicates. Most publications were excluded after the title and abstract analysis ( n = 860). Among the 28 studies selected for full-text screening, 10 were excluded for the reasons described in Additional file 3 , and 18 were included in the final analysis (Fig. 1 ) [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Reference list screening did not retrieve any additional systematic reviews.

PRISMA flow diagram

Characteristics of included reviews

Summary features of 18 systematic reviews are presented in Table 1 . They were published in 14 different journals. Only four of these journals had specific requirements for systematic reviews (with or without meta-analysis): European Journal of Internal Medicine, Journal of Clinical Medicine, Ultrasound in Obstetrics and Gynecology, and Clinical Research in Cardiology . Two journals reported that they published only invited reviews ( Journal of Medical Virology and Clinica Chimica Acta ). Three systematic reviews in our study were published as letters; one was labeled as a scoping review and another as a rapid review (Table 2 ).

All reviews were published in English, in first quartile (Q1) journals, with JIF ranging from 1.692 to 6.062. One review was empty, meaning that its search did not identify any relevant studies; i.e., no primary studies were included [ 36 ]. The remaining 17 reviews included 269 unique studies; the majority ( N = 211; 78%) were included in only a single review included in our study (range: 1 to 12). Primary studies included in the reviews were published between December 2019 and March 18, 2020, and comprised case reports, case series, cohorts, and other observational studies. We found only one review that included randomized clinical trials [ 38 ]. In the included reviews, systematic literature searches were performed from 2019 (entire year) up to March 9, 2020. Ten systematic reviews included meta-analyses. The list of primary studies found in the included systematic reviews is shown in Additional file 4 , as well as the number of reviews in which each primary study was included.

Population and study designs

Most of the reviews analyzed data from patients with COVID-19 who developed pneumonia, acute respiratory distress syndrome (ARDS), or any other correlated complication. One review aimed to evaluate the effectiveness of using surgical masks on preventing transmission of the virus [ 36 ], one review was focused on pediatric patients [ 34 ], and one review investigated COVID-19 in pregnant women [ 37 ]. Most reviews assessed clinical symptoms, laboratory findings, or radiological results.

Systematic review findings

The summary of findings from individual reviews is shown in Table 2 . Overall, all-cause mortality ranged from 0.3 to 13.9% (Fig. 2 ).

A meta-analysis of the prevalence of mortality

Clinical symptoms

Seven reviews described the main clinical manifestations of COVID-19 [ 26 , 28 , 29 , 34 , 35 , 39 , 41 ]. Three of them provided only a narrative discussion of symptoms [ 26 , 34 , 35 ]. In the reviews that performed a statistical analysis of the incidence of different clinical symptoms, symptoms in patients with COVID-19 were (range values of point estimates): fever (82–95%), cough with or without sputum (58–72%), dyspnea (26–59%), myalgia or muscle fatigue (29–51%), sore throat (10–13%), headache (8–12%), gastrointestinal disorders, such as diarrhea, nausea or vomiting (5.0–9.0%), and others (including, in one study only: dizziness 12.1%) (Figs. 3 , 4 , 5 , 6 , 7 , 8 and 9 ). Three reviews assessed cough with and without sputum together; only one review assessed sputum production itself (28.5%).

A meta-analysis of the prevalence of fever

A meta-analysis of the prevalence of cough

A meta-analysis of the prevalence of dyspnea

A meta-analysis of the prevalence of fatigue or myalgia

A meta-analysis of the prevalence of headache

A meta-analysis of the prevalence of gastrointestinal disorders

A meta-analysis of the prevalence of sore throat

Diagnostic aspects

Three reviews described methodologies, protocols, and tools used for establishing the diagnosis of COVID-19 [ 26 , 34 , 38 ]. The use of respiratory swabs (nasal or pharyngeal) or blood specimens to assess the presence of SARS-CoV-2 nucleic acid using RT-PCR assays was the most commonly used diagnostic method mentioned in the included studies. These diagnostic tests have been widely used, but their precise sensitivity and specificity remain unknown. One review included a Chinese study with clinical diagnosis with no confirmation of SARS-CoV-2 infection (patients were diagnosed with COVID-19 if they presented with at least two symptoms suggestive of COVID-19, together with laboratory and chest radiography abnormalities) [ 34 ].

Therapeutic possibilities

Pharmacological and non-pharmacological interventions (supportive therapies) used in treating patients with COVID-19 were reported in five reviews [ 25 , 27 , 34 , 35 , 38 ]. Antivirals used empirically for COVID-19 treatment were reported in seven reviews [ 25 , 27 , 34 , 35 , 37 , 38 , 41 ]; most commonly used were protease inhibitors (lopinavir, ritonavir, darunavir), nucleoside reverse transcriptase inhibitor (tenofovir), nucleotide analogs (remdesivir, galidesivir, ganciclovir), and neuraminidase inhibitors (oseltamivir). Umifenovir, a membrane fusion inhibitor, was investigated in two studies [ 25 , 35 ]. Possible supportive interventions analyzed were different types of oxygen supplementation and breathing support (invasive or non-invasive ventilation) [ 25 ]. The use of antibiotics, both empirically and to treat secondary pneumonia, was reported in six studies [ 25 , 26 , 27 , 34 , 35 , 38 ]. One review specifically assessed evidence on the efficacy and safety of the anti-malaria drug chloroquine [ 27 ]. It identified 23 ongoing trials investigating the potential of chloroquine as a therapeutic option for COVID-19, but no verifiable clinical outcomes data. The use of mesenchymal stem cells, antifungals, and glucocorticoids were described in four reviews [ 25 , 34 , 35 , 38 ].

Laboratory and radiological findings

Of the 18 reviews included in this overview, eight analyzed laboratory parameters in patients with COVID-19 [ 25 , 29 , 30 , 32 , 33 , 34 , 35 , 39 ]; elevated C-reactive protein levels, associated with lymphocytopenia, elevated lactate dehydrogenase, as well as slightly elevated aspartate and alanine aminotransferase (AST, ALT) were commonly described in those eight reviews. Lippi et al. assessed cardiac troponin I (cTnI) [ 25 ], procalcitonin [ 32 ], and platelet count [ 33 ] in COVID-19 patients. Elevated levels of procalcitonin [ 32 ] and cTnI [ 30 ] were more likely to be associated with a severe disease course (requiring intensive care unit admission and intubation). Furthermore, thrombocytopenia was frequently observed in patients with complicated COVID-19 infections [ 33 ].

Chest imaging (chest radiography and/or computed tomography) features were assessed in six reviews, all of which described a frequent pattern of local or bilateral multilobar ground-glass opacity [ 25 , 34 , 35 , 39 , 40 , 41 ]. Those six reviews showed that septal thickening, bronchiectasis, pleural and cardiac effusions, halo signs, and pneumothorax were observed in patients suffering from COVID-19.

Quality of evidence in individual systematic reviews

Table 3 shows the detailed results of the quality assessment of 18 systematic reviews, including the assessment of individual items and summary assessment. A detailed explanation for each decision in each review is available in Additional file 5 .

Using AMSTAR 2 criteria, confidence in the results of all 18 reviews was rated as “critically low” (Table 3 ). Common methodological drawbacks were: omission of prospective protocol submission or publication; use of inappropriate search strategy: lack of independent and dual literature screening and data-extraction (or methodology unclear); absence of an explanation for heterogeneity among the studies included; lack of reasons for study exclusion (or rationale unclear).

Risk of bias assessment, based on a reported methodological tool, and quality of evidence appraisal, in line with the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) method, were reported only in one review [ 25 ]. Five reviews presented a table summarizing bias, using various risk of bias tools [ 25 , 29 , 39 , 40 , 41 ]. One review analyzed “study quality” [ 37 ]. One review mentioned the risk of bias assessment in the methodology but did not provide any related analysis [ 28 ].

This overview of systematic reviews analyzed the first 18 systematic reviews published after the onset of the COVID-19 pandemic, up to March 24, 2020, with primary studies involving more than 60,000 patients. Using AMSTAR-2, we judged that our confidence in all those reviews was “critically low”. Ten reviews included meta-analyses. The reviews presented data on clinical manifestations, laboratory and radiological findings, and interventions. We found no systematic reviews on the utility of diagnostic tests.

Symptoms were reported in seven reviews; most of the patients had a fever, cough, dyspnea, myalgia or muscle fatigue, and gastrointestinal disorders such as diarrhea, nausea, or vomiting. Olfactory dysfunction (anosmia or dysosmia) has been described in patients infected with COVID-19 [ 43 ]; however, this was not reported in any of the reviews included in this overview. During the SARS outbreak in 2002, there were reports of impairment of the sense of smell associated with the disease [ 44 , 45 ].

The reported mortality rates ranged from 0.3 to 14% in the included reviews. Mortality estimates are influenced by the transmissibility rate (basic reproduction number), availability of diagnostic tools, notification policies, asymptomatic presentations of the disease, resources for disease prevention and control, and treatment facilities; variability in the mortality rate fits the pattern of emerging infectious diseases [ 46 ]. Furthermore, the reported cases did not consider asymptomatic cases, mild cases where individuals have not sought medical treatment, and the fact that many countries had limited access to diagnostic tests or have implemented testing policies later than the others. Considering the lack of reviews assessing diagnostic testing (sensitivity, specificity, and predictive values of RT-PCT or immunoglobulin tests), and the preponderance of studies that assessed only symptomatic individuals, considerable imprecision around the calculated mortality rates existed in the early stage of the COVID-19 pandemic.

Few reviews included treatment data. Those reviews described studies considered to be at a very low level of evidence: usually small, retrospective studies with very heterogeneous populations. Seven reviews analyzed laboratory parameters; those reviews could have been useful for clinicians who attend patients suspected of COVID-19 in emergency services worldwide, such as assessing which patients need to be reassessed more frequently.

All systematic reviews scored poorly on the AMSTAR 2 critical appraisal tool for systematic reviews. Most of the original studies included in the reviews were case series and case reports, impacting the quality of evidence. Such evidence has major implications for clinical practice and the use of these reviews in evidence-based practice and policy. Clinicians, patients, and policymakers can only have the highest confidence in systematic review findings if high-quality systematic review methodologies are employed. The urgent need for information during a pandemic does not justify poor quality reporting.

We acknowledge that there are numerous challenges associated with analyzing COVID-19 data during a pandemic [ 47 ]. High-quality evidence syntheses are needed for decision-making, but each type of evidence syntheses is associated with its inherent challenges.

The creation of classic systematic reviews requires considerable time and effort; with massive research output, they quickly become outdated, and preparing updated versions also requires considerable time. A recent study showed that updates of non-Cochrane systematic reviews are published a median of 5 years after the publication of the previous version [ 48 ].

Authors may register a review and then abandon it [ 49 ], but the existence of a public record that is not updated may lead other authors to believe that the review is still ongoing. A quarter of Cochrane review protocols remains unpublished as completed systematic reviews 8 years after protocol publication [ 50 ].

Rapid reviews can be used to summarize the evidence, but they involve methodological sacrifices and simplifications to produce information promptly, with inconsistent methodological approaches [ 51 ]. However, rapid reviews are justified in times of public health emergencies, and even Cochrane has resorted to publishing rapid reviews in response to the COVID-19 crisis [ 52 ]. Rapid reviews were eligible for inclusion in this overview, but only one of the 18 reviews included in this study was labeled as a rapid review.

Ideally, COVID-19 evidence would be continually summarized in a series of high-quality living systematic reviews, types of evidence synthesis defined as “ a systematic review which is continually updated, incorporating relevant new evidence as it becomes available ” [ 53 ]. However, conducting living systematic reviews requires considerable resources, calling into question the sustainability of such evidence synthesis over long periods [ 54 ].

Research reports about COVID-19 will contribute to research waste if they are poorly designed, poorly reported, or simply not necessary. In principle, systematic reviews should help reduce research waste as they usually provide recommendations for further research that is needed or may advise that sufficient evidence exists on a particular topic [ 55 ]. However, systematic reviews can also contribute to growing research waste when they are not needed, or poorly conducted and reported. Our present study clearly shows that most of the systematic reviews that were published early on in the COVID-19 pandemic could be categorized as research waste, as our confidence in their results is critically low.

Our study has some limitations. One is that for AMSTAR 2 assessment we relied on information available in publications; we did not attempt to contact study authors for clarifications or additional data. In three reviews, the methodological quality appraisal was challenging because they were published as letters, or labeled as rapid communications. As a result, various details about their review process were not included, leading to AMSTAR 2 questions being answered as “not reported”, resulting in low confidence scores. Full manuscripts might have provided additional information that could have led to higher confidence in the results. In other words, low scores could reflect incomplete reporting, not necessarily low-quality review methods. To make their review available more rapidly and more concisely, the authors may have omitted methodological details. A general issue during a crisis is that speed and completeness must be balanced. However, maintaining high standards requires proper resourcing and commitment to ensure that the users of systematic reviews can have high confidence in the results.

Furthermore, we used adjusted AMSTAR 2 scoring, as the tool was designed for critical appraisal of reviews of interventions. Some reviews may have received lower scores than actually warranted in spite of these adjustments.

Another limitation of our study may be the inclusion of multiple overlapping reviews, as some included reviews included the same primary studies. According to the Cochrane Handbook, including overlapping reviews may be appropriate when the review’s aim is “ to present and describe the current body of systematic review evidence on a topic ” [ 12 ], which was our aim. To avoid bias with summarizing evidence from overlapping reviews, we presented the forest plots without summary estimates. The forest plots serve to inform readers about the effect sizes for outcomes that were reported in each review.

Several authors from this study have contributed to one of the reviews identified [ 25 ]. To reduce the risk of any bias, two authors who did not co-author the review in question initially assessed its quality and limitations.

Finally, we note that the systematic reviews included in our overview may have had issues that our analysis did not identify because we did not analyze their primary studies to verify the accuracy of the data and information they presented. We give two examples to substantiate this possibility. Lovato et al. wrote a commentary on the review of Sun et al. [ 41 ], in which they criticized the authors’ conclusion that sore throat is rare in COVID-19 patients [ 56 ]. Lovato et al. highlighted that multiple studies included in Sun et al. did not accurately describe participants’ clinical presentations, warning that only three studies clearly reported data on sore throat [ 56 ].

In another example, Leung [ 57 ] warned about the review of Li, L.Q. et al. [ 29 ]: “ it is possible that this statistic was computed using overlapped samples, therefore some patients were double counted ”. Li et al. responded to Leung that it is uncertain whether the data overlapped, as they used data from published articles and did not have access to the original data; they also reported that they requested original data and that they plan to re-do their analyses once they receive them; they also urged readers to treat the data with caution [ 58 ]. This points to the evolving nature of evidence during a crisis.

Our study’s strength is that this overview adds to the current knowledge by providing a comprehensive summary of all the evidence synthesis about COVID-19 available early after the onset of the pandemic. This overview followed strict methodological criteria, including a comprehensive and sensitive search strategy and a standard tool for methodological appraisal of systematic reviews.

In conclusion, in this overview of systematic reviews, we analyzed evidence from the first 18 systematic reviews that were published after the emergence of COVID-19. However, confidence in the results of all the reviews was “critically low”. Thus, systematic reviews that were published early on in the pandemic could be categorized as research waste. Even during public health emergencies, studies and systematic reviews should adhere to established methodological standards to provide patients, clinicians, and decision-makers trustworthy evidence.

Availability of data and materials

All data collected and analyzed within this study are available from the corresponding author on reasonable request.

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Acknowledgments

We thank Catherine Henderson DPhil from Swanscoe Communications for pro bono medical writing and editing support. We acknowledge support from the Covidence Team, specifically Anneliese Arno. We thank the whole International Network of Coronavirus Disease 2019 (InterNetCOVID-19) for their commitment and involvement. Members of the InterNetCOVID-19 are listed in Additional file 6 . We thank Pavel Cerny and Roger Crosthwaite for guiding the team supervisor (IJBN) on human resources management.

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Israel Júnior Borges do Nascimento & Milena Soriano Marcolino

Medical College of Wisconsin, Milwaukee, WI, USA

Israel Júnior Borges do Nascimento

Helene Fuld Health Trust National Institute for Evidence-based Practice in Nursing and Healthcare, College of Nursing, The Ohio State University, Columbus, OH, USA

Dónal P. O’Mathúna

School of Nursing, Psychotherapy and Community Health, Dublin City University, Dublin, Ireland

Department of Anesthesiology, Intensive Care and Pain Medicine, University of Münster, Münster, Germany

Thilo Caspar von Groote

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Hebatullah Mohamed Abdulazeem

School of Health Sciences, Faculty of Health and Medicine, The University of Newcastle, Callaghan, Australia

Ishanka Weerasekara

Department of Physiotherapy, Faculty of Allied Health Sciences, University of Peradeniya, Peradeniya, Sri Lanka

Cochrane Croatia, University of Split, School of Medicine, Split, Croatia

Ana Marusic, Irena Zakarija-Grkovic & Tina Poklepovic Pericic

Center for Evidence-Based Medicine and Health Care, Catholic University of Croatia, Ilica 242, 10000, Zagreb, Croatia

Livia Puljak

Cochrane Brazil, Evidence-Based Health Program, Universidade Federal de São Paulo, São Paulo, Brazil

Vinicius Tassoni Civile & Alvaro Nagib Atallah

Yorkville University, Fredericton, New Brunswick, Canada

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IJBN conceived the research idea and worked as a project coordinator. DPOM, TCVG, HMA, IW, AM, LP, VTC, IZG, TPP, ANA, SF, NLB and MSM were involved in data curation, formal analysis, investigation, methodology, and initial draft writing. All authors revised the manuscript critically for the content. The author(s) read and approved the final manuscript.

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Supplementary Information

Additional file 1: appendix 1..

Search strategies used in the study.

Additional file 2: Appendix 2.

Adjusted scoring of AMSTAR 2 used in this study for systematic reviews of studies that did not analyze interventions.

Additional file 3: Appendix 3.

List of excluded studies, with reasons.

Additional file 4: Appendix 4.

Table of overlapping studies, containing the list of primary studies included, their visual overlap in individual systematic reviews, and the number in how many reviews each primary study was included.

Additional file 5: Appendix 5.

A detailed explanation of AMSTAR scoring for each item in each review.

Additional file 6: Appendix 6.

List of members and affiliates of International Network of Coronavirus Disease 2019 (InterNetCOVID-19).

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Borges do Nascimento, I.J., O’Mathúna, D.P., von Groote, T.C. et al. Coronavirus disease (COVID-19) pandemic: an overview of systematic reviews. BMC Infect Dis 21 , 525 (2021). https://doi.org/10.1186/s12879-021-06214-4

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DOI : https://doi.org/10.1186/s12879-021-06214-4

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June 28, 2021

As the COVID-19 pandemic continues to evolve, various Harvard restrictions and processes that were in place have now been re-visited. Moving forward, take the following into consideration when conducting research with human subjects:

• All research and on-campus activity, should still follow Harvard and local school/department guidelines. For instance, this means that personnel who have not yet been authorized to work on campus will need to check with their departments (or divisions or schools) about the appropriate process to obtain authorization prior to the August 2 nd general return date.
• the most up to date University guidance
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• Note that Harvard continues to require masks indoors, regardless of vaccination status. This guidance will be updated as Harvard requirements and local community incidence changes. Please also check local school or division for more local guidance.
• Some previous restrictions placed on human subjects research have been lifted. Currently physical distancing is no longer required for those vaccinated in all research locations. Please check with your school/division/department for any local guidelines.
• Irrespective of location, individuals interacting with human subjects are advised to continue to wear surgical masks as vaccination status of study participants cannot be assumed. Research study personnel should let participants decide if they would like to wear a mask if the study procedures allow it.
• Researchers may wish to inform their study population of the current COVID-19 status on campus , or in the study location if elsewhere , including level of community transmission of COVID-19 and COVID-19 vaccination coverage.  It continues to be recommended that those that are unvaccinated and at high-risk for COVID-19 complications or immunocompromised not take part in research.
• It is recommended that researchers conduct a brief screening with study participants prior to the study visit. Sample questions may be found below.
• Other restrictions such as those involving travel and working in other locations or at other institutions are still in place. It is important for researchers to follow any guidelines or instructions from the specific facility or location where in-person research would occur. As some research may occur in another state, with another institution, or under the direction of another IRB (as in a reliance agreement situation), this is especially important.  It is the responsibility of the Study Team to keep apprised of potential restrictions and conduct their study accordingly.
• Researchers planning to hire professional companies (survey organization and the like) in other states or countries should do due diligence to make sure that these organizations are taking reasonable coronavirus precautions and are fully aware of local conditions and government restrictions. In particular, Harvard should not be asking these organizations to be engaging in practices that are riskier than their normal business operations.

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You may access the archive of COVID-19 research information, research restrictions and processes here - https://cuhs.harvard.edu/questions-about-covid-19-and-your-research-ARCHIVE

Sample questions for COVID-19 screening https://projects.iq.harvard.edu/files/scictr/files/crimson_clear_paperform_as_of_06072020.pdf

Q1: ARE YOU EXPERIENCING ANY OF THE FOLLOWING SYMPTOMS? (CHECK ALL THAT APPLY)

☐ Fever, chills, or feeling feverish

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☐ Shortness of breath or difficulty breathing

☐ New fatigue

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☐ New headache

☐ New loss of taste or smell

☐ Sore throat

☐ New nasal congestion or new runny nose (not related to seasonal allergies)

☐ Nausea or vomiting

☐ Diarrhea  

If ANY of the above apply, inform the study participant that they will not be permitted to come to the study visit on that day and that they should contact their health care provider. For medical emergencies, call 911.

If NONE of the above apply, proceed to Q2

Q2: IN THE LAST 14 DAYS, HAVE YOU BEEN IN CLOSE CONTACT WITH ANYONE WHO HAS TESTED POSITIVE FOR COVID-19? (CHECK BOX)

If Yes, the study participant believes that they were exposed to a confirmed case of COVID-19, inform them that they will not be permitted to attend the study visit on that day and that they should contact their health care provider. For medical emergencies, call 911.

If No, inform study participant that they may come to the study visit. Remind them to always wear a facemask as well as any location or study specific information that they should know about.

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15 Common Coronavirus (COVID-19) Questions

See the research behind everything you've been Googling

By now, you may understand the basics of COVID-19 : It’s a respiratory disease caused by a new virus, SARS-CoV-2, to which humans do not have immunity. And it’s spreading fast enough to be called a pandemic . But there are still plenty of unknowns and plenty of rumors. We’ve rounded up some of the questions we’ve been hearing that can be answered at this time. 

How can you get tested for COVID-19?

You need a doctor’s order to get a COVID-19 swab test. But even if your doctor would like to have you tested, a limited number of tests and overcrowded healthcare facilities have made the criteria for getting tested quite strict. Displaying symptoms like a cough or fever is generally not enough in an otherwise healthy person to warrant a test. Those who are already hospitalized, who have chronic conditions, or have been recently exposed to an infected person or region will take priority.  

Regardless of whether or not you think you’re eligible for a test, if you’re concerned about having COVID-19, you should contact your healthcare provider. They can tell you the appropriate next steps based on your history and the area where you live. More tests are being developed, and the goal is to test everybody who needs to be tested. Use our printable Doctor Discussion Guide below to help prepare for your appointment.

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Is loss of smell a COVID-19 symptom that warrants a doctor's appointment?

A statement released on March 21 by ENT UK at The Royal College of Surgeons of England  suggests that anosmia, or the loss of the sense of smell, occurs in significant numbers of COVID-19 cases, and may even be the only symptom in some patients. Author Claire Hopkins, President of the British Rhinological Society, suggests anosmia "could be used as a screening tool to help identify otherwise asymptomatic patients, who could then be better instructed on self-isolation."

Hopkins concedes many people with anosmia probably just have typical rhinovirus and coronavirus strains—in other words, the common cold. Regardless, asking everyone who has lost their sense of smell to self-isolate would be one more important way to stop COVID-19 transmission.

With that in mind, self-isolation is a good place to start if you've lost your sense of smell, rather than heading to the doctor's office.

"While the UK ENT information regarding loss of smell and/or taste is interesting, it is not something we could offer a test for at this time," Kristin Englund, MA, an adult infectious diseases specialist with Cleveland Clinic, tells Verywell. "We are prioritizing high-risk patients for testing. If a person experiences anosmia, it is reasonable to distance themselves from others, especially those over age 60 and those with chronic medical illnesses, as the symptom could indicate any number of viruses, including COVID-19."

How long does COVID-19 live on different surfaces?

A study published in The New England Journal of Medicine offers the following timeframes for how long the SARS-CoV-2 virus (which causes the COVID-19 disease) can remain viable on various surfaces:  

Aerosols (fine droplets suspended in air): 3 hours

Copper: 4 hours

Cardboard: 24 hours

Plastic: 3 days

Stainless steel: 3 days

Is it true that ibuprofen is unsafe to take if you think you have COVID-19 symptoms?

This rumor’s origin and resolution (at least for now) can both be found on Twitter. On March 14, French health minister Olivier Véran tweeted a warning that ibuprofen could potentially worsen symptoms of COVID-19. His tweet followed the publication of an article in the medical journal The Lancet . While the scope of the article was about the link between both high blood pressure and diabetes and COVID-19, it mentioned that an enzyme called ACE2—which coronaviruses use to bind to cells—can increase in amount when you take ibuprofen. In other words, the article suggested taking ibuprofen would increase the number of enzymes the COVID-19 virus had the opportunity to bind to. 

Currently, there is not enough research to back this idea. While many articles claimed WHO advised against ibuprofen, its only official statement—issued on Twitter on March 18—says otherwise.

“At present, based on currently available information, WHO does not recommend against the use of ibuprofen. We are also consulting with physicians treating COVID-19 patients and are not aware of reports of any negative effects of ibuprofen, beyond the usual known side effects that limit its use in certain populations. WHO is not aware of published clinical or population-based data on this topic.” — World Health Organization

Is it true that only someone with COVID-19 symptoms can pass it on?

The World Health Organization (WHO) director-general previously suggested people already displaying COVID-19 symptoms—such as coughing, fever, or shortness of breath—were the biggest drivers of viral transmission. In other words, if you’re not showing symptoms, it’s not likely you can pass the virus on. The Centers for Disease Control and Prevention (CDC) backs this idea, adding that some spread may be possible before people show symptoms, although that’s not the main way the virus spreads.  It's estimated that 25% of people with COVID-19 are asymptomatic.

One example of potential COVID-19 spread prior to symptoms includes the Biogen company meeting in Boston, Massachusetts, which has been pinpointed as the source of most cases in the state. Over 100 employees from all over the world—and now, their close contacts—have tested positive for COVID-19 in the days and weeks after attending the meeting. Supposedly, nobody showed symptoms during the two-day conference in February where it initially spread. An investigation into the conference—as well as a closer look at symptom status—is ongoing.

Globally, researchers are highlighting other examples of COVID-19 transmission that may have occurred before people showed symptoms. While published ahead of peer-review and print, an analysis of data from Singapore suggests 48% of cases resulted from pre-symptomatic transmission. The same study puts that statistic at 62% for cases in Tianjin, China.

Should you cancel any routine doctor’s appointments unrelated to COVID-19?

Healthcare providers have mixed opinions on keeping routine appointments right now, and it may depend on where you live. As for Dr. Khabbaza? He recommends rescheduling or trying telemedicine.

“We would recommend, for the time being, cancelling all non-essential in-person doctor's appointments,” he says. “Many health systems are now providing free virtual visits to take the place of the office visits, allowing you to see your doctor from home. If virtual options are not available with your doctor, check with them to see if they feel it is appropriate for you to push back your appointment. This advice holds especially true for those older than 60, but I would advise anyone to avoid healthcare facilities unless truly needed.”

Is COVID-19 going to become seasonal? Can you get it twice in one season?

The 2009 swine flu pandemic occurred because of an outbreak of a new type of influenza A virus: H1N1. But now, H1N1 is considered a normal type of seasonal flu. Since COVID-19 is the result of a new type of coronavirus—SARS-CoV-2—it’s logical to think the same thing might happen, and that it could become less severe in years to come. But experts think it’s too soon to say.

“As of now, it is too early for us to know if this will be a seasonal virus that changes slightly from year to year like influenza does,” Joseph Khabbaza, MD, a pulmonologist at Cleveland Clinic, tells Verywell. “If similar to other respiratory viruses, it is unlikely to get COVID-19 twice in one season.”

What does “flattening the curve” mean?

Either the phrase “flattening the curve” or an image of the curve itself might be familiar. The origin of this graph is pretty complex; a population health analyst named Drew A. Harris, DPM, MPH, pulled information from a CDC paper, The Economist , and his own experience as a pandemic preparedness instructor to create it. But the concept behind it is relatively simple. 

Without the proper protections in place, our society will see a sudden spike in COVID-19 cases that is way too high for our healthcare systems to facilitate. As a result, not everyone will get adequate treatment, and more people will die. The alternative? Put protective measures in place—like social distancing—that prevent that spike from happening. COVID-19 will spread more slowly, allowing doctors, researchers, and other healthcare professionals enough time and resources to react. The duration of the virus in the community will be longer, but it will be more manageable.

What does it mean to "shelter in place?”

Sheltering in place is a safety precaution that is sometimes used in conjunction with natural disasters or other emergencies. Generally, people are asked to remain in an indoor location until it is safe to go outside. If you and your loved ones are asked to "shelter in place" in connection with COVID-19, this means that you should stay home unless you need to go outside for an essential reason, such as to get food or seek medical aid. If you have an essential job, you may be asked to still commute to work.

You should not congregate in groups, and you should stay at least six feet away from others outside your home. Your local government's instructions will provide more detailed information. Some communities in the U.S., including San Francisco , have asked community members to shelter in place as a way to limit the amount of possible COVID-19 infections. Staying put indoors helps communities stay safe as a whole.

Can kids get COVID-19?

While children can get COVID-19 both the WHO and the CDC report they’re much less likely to contract it than adults. If they do, symptoms will be the same, but will likely be milder, and could potentially include diarrhea and vomiting.

Adults should be less concerned about catching COVID-19 from a child than they should be about potentially spreading it to a child. According to the WHO , “preliminary data from household transmission studies in China suggest that children are infected from adults, rather than vice versa.”

Can pets infect humans with COVID-19?

COVID-19 is part of a larger group of coronaviruses. Some viruses in this group can cause illness in animals, including livestock, camels, and bats. While it's rare, those infections can spread to humans, as was the case with older coronaviruses SARS and MERS. Is animal to human transmission also possible with COVID-19?

While it's possible (but unconfirmed) that COVID-19 originally spread from an animal to a human, the CDC has no evidence that livestock, wild animals, or pets are causing its spread in the U.S. at this time.

But what about the other way around: Can people spread COVID-19 to animals? The confirmed case in a Bronx Zoo tiger says yes; the tiger contracted the disease from a zookeeper.

Two cats in two different areas of New York State marked the first confirmed cases of COVID-19 in pets in the U.S., the CDC announced on April 22. Both are expected to make a full recovery. Only one is owned by a human who tested positive for COVID-19.

A pug owned by a North Carolina family infected with COVID-19 is the first known dog in the US to test positive for the disease. The family participated in Duke University's Molecular and Epidemiological Study of Suspected Infection (MESSI). The dog's symptoms—sneezing and a lack of appetite—only lasted for a few days.

The CDC maintains it is still very unlikely that pets can pass COVID-19 to humans. For the safety of your pets, do not let them interact with people or other animals outside of your household at this time.

It is not uncommon for cats and dogs to get their own strains of coronavirus: feline coronavirus and canine coronavirus. However, these are short-lived intestinal infections with no link to COVID-19 and no risk to humans.

Is food delivery safe right now?

While we can’t be the judge of whether or not your favorite local restaurant is taking all necessary sanitary precautions, we can ask a doctor for their opinion. 

“Having food delivered is felt to be safe at this time, but an emphasis on disinfecting and avoiding close contact with people remains,” Dr. Khabbaza says. He offers three tips for food delivery:

• Ask to have the food delivered to your doorstep rather than directly handed to you
• Wipe down any food container with a disinfectant 
• Wash your hands immediately after accepting the delivery and handling the container

Can mosquitos transmit COVID-19?

According to the WHO, there is no evidence that mosquitos can pass on COVID-19.   It's a respiratory disease, not a blood-borne disease, and is currently known to spread through droplets discharged by coughing, sneezing, and runny noses.

Are swimming pools safe?

The CDC says there is no evidence that COVID-19 can be spread through pools and hot tubs. Normal care and maintenance, like using chlorine or bromine, should inactivate or remove any viruses.

Can COVID-19 live in hotter climates?

While no studies on this subject have been peer-reviewed yet—meaning they still need to be vetted for validity—a few suggest that COVID-19 seems to thrive within a cooler temperature range. 

For example, researchers from the Massachusetts Institute of Technology report that the majority of COVID-19 transmissions globally have occurred between 3°C and 13°C (37.4 to 55.4°F). Fewer than 5% of cases have occurred in areas where average temperatures were greater than 18°C (64.4°F) throughout January, February, and March.

According to the MIT researchers, “the north-south divide observed in the U.S. further suggests that transmission of 2019-nCoV virus might be less efficient at warmer temperatures and therefore with approaching summer temperatures in the Northern Hemisphere, the spread of 2019-nCoV might decline in the next few months.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page .

Centers for Disease Control and Prevention. Evaluating and testing persons for coronavirus disease 2019 (COVID-19) .

Van doremalen N, Bushmaker T, Morris DH, et al. Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 . N Engl J Med . 2020;382:1564-1567. doi:10.1056/NEJMc2004973

Fang L, Karakiulakis G, Roth M. Are patients with hypertension and diabetes mellitus at increased risk for COVID-19 infection? The Lancet . March 11, 2020;8(4):E21. doi:10.1016/S2213-2600(20)30116-8

World Health Organization. WHO Director-General's opening remarks at the media briefing on COVID-19 .

Centers for Disease Control and Prevention. Coronavirus Disease 2019 (COVID-19): How it spreads .

CDC Director On Models For The Months To Come: 'This Virus Is Going To Be With Us.' NPR.

Massachusetts Department of Public Health. Coronavirus Disease 2019 (COVID-19) Cases in MA .

Ganyani T, Kremer C, Chen D, et al. Estimating the generation interval for COVID-19 based on symptom onset data . MedRxiv . Preprint. doi:10.1101/2020.03.05.20031815

Centers for Disease Control and Prevention. 2009 H1N1 Pandemic (H1N1pdm09 virus) .

Qualls N, Levitt A, Kanade N, et al. Community Mitigation Guidelines to Prevent Pandemic Influenza — United States, 2017 . Recommendations and Reports. 2017;66(1):1–34.

Roberts S. Flatting the coronavirus curve . The New York Times .

Centers for Disease Control and Prevention. Emergency preparedness and response: Stay put - learn how to shelter in place .

Centers for Disease Control and Prevention. Coronavirus Disease-2019 (COVID-19) and Children .

World Health Organization. Coronavirus disease 2019 (COVID-19)

Situation Report – 46 .

Centers for Disease Control and Prevention. Animals and coronavirus disease 2019 (COVID-19) .

Wildlife Conservation Society. A Tiger at Bronx Zoo Tests Positive for COVID-19; The Tiger and the Zoo’s Other Cats Are Doing Well at This Time .

Centers for Disease Control and Prevention. Confirmation of COVID-19 in Two Pet Cats in New York .

Chapel Hill pug tests positive for virus that causes COVID-19; first known case in a dog in the US . WRAL.com .

World Health Organization. Coronavirus disease (COVID-19) advice for the public: Myth busters .

Centers for Disease Control and Prevention. Water transmission and COVID-19 .

Bukhari Q, Jameel Y. Will coronavirus pandemic diminish by summer? SSRN .

By Anisa Arsenault Anisa joined the company in 2018 after managing news surrounding fertility, pregnancy, and parenting for The Bump. Her health and wellness articles have appeared in outlets like Prevention and Metro US. At Verywell, she is responsible for the news program, which includes coverage of COVID-19.

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Air Cleaners, HVAC Filters, and Coronavirus (COVID-19)

Portable air cleaners (also known as air purifiers) may be particularly helpful when additional ventilation with outdoor air is not possible without compromising indoor comfort (temperature or humidity), or when outdoor air pollution is high.

Caution: The use of air cleaners alone cannot ensure adequate indoor air quality, particularly where significant pollutant sources are present and ventilation is insufficient. Read EPA’s “Guide to air cleaners in the home" (PDF).

When used properly, air cleaners and HVAC filters can help reduce airborne contaminants including viruses in a building or small space. By itself, air cleaning or filtration is not enough to protect people from COVID-19. When used along with other best practices recommended by CDC and other public health agencies, including social distancing and mask wearing, filtration can be part of a plan to reduce the potential for airborne transmission of COVID-19 indoors.

Air cleaners and HVAC filters are designed to filter pollutants or contaminants out of the air that passes thru them. Air cleaning and filtration can help reduce airborne contaminants, including particles containing viruses. 

In order for an air cleaner to be effective in removing viruses from the air, it must be able to remove small airborne particles (in the size range of 0.1-1 um). Manufacturers report this capability in several ways. In some cases, they may indicate particle removal efficiency for specific particle sizes (e.g. “removes 99.9% of particles as small as 0.3 um”). Many manufacturers use the Clean Air Delivery Rate (CADR) rating system to rate air cleaner performance. Others indicate they use High Efficiency Particulate Air (HEPA) filters. In order to select an air cleaner that effectively filters viruses from the air, choose: 1) a unit that is the right size for the space you will be using it in (this is typically indicated by the manufacturer in square feet), 2) a unit that has a high CADR for smoke (vs. pollen or dust), is designated a HEPA unit, or specifically indicates that it filters particles in the 0.1-1 um size range.

Air Cleaners and HVAC Filters in Homes

Choose a portable air cleaner that is intended for the room size in which it will be used and be sure it meets at least one of the following criteria:

• it is designated as High-Efficiency Particulate Air (HEPA),
• it is CADR rated for smoke, or
• the manufacturer states that the device will remove most particles in the size range below 1 um.

Most manufacturers provide this information on the air cleaner packaging, label or website description.

Do not use air cleaners that intentionally generate ozone in occupied spaces or that do not meet state regulations or industry standards for ozone generation.

Where to place a portable air cleaner in your home

Choosing where in your home to place a portable air cleaner to help protect from airborne infections depends on the situation. Put the air cleaner in the room where most people spend most of their time (e.g., a living room or bedroom) unless: 

• Someone in a household is especially vulnerable to the risks from infection, then, place the air cleaner where they spend most of their time or
• If someone is isolating because of an active infection, then, place the air cleaner where they are isolating.  See CDC Website 
• Read  EPA’s “Guide to air cleaners in the home”  for more information on HVAC filters and placing and operating a portable air cleaner.
• Use CDC's  Interactive Ventilation Tool  to learn how to decrease levels of virus particles during and after a guest visits a home.

Air Cleaners and HVAC Filters in Offices, Schools, and Commercial Buildings

The HVAC systems of large buildings typically filter air before it is distributed throughout a building, so consider upgrading HVAC filters as appropriate for your specific building and HVAC system (consult an HVAC professional). The variety and complexity of HVAC systems in large buildings requires professional interpretation of technical guidelines, such as those provided by ASHRAE and CDC . EPA, ASHRAE and CDC recommend upgrading air filters to the highest efficiency possible that is compatible with the system and checking the filter fit to minimize filter air bypass.

Consider using portable air cleaners to supplement increased HVAC system ventilation and filtration, especially in areas where adequate ventilation is difficult to achieve. Directing the airflow so that it does not blow directly from one person to another reduces the potential spread of droplets that may contain infectious viruses.

Air cleaning may be useful when used along with source control and ventilation, but it is not a substitute for either method. Source control involves removing or decreasing pollutants such as smoke, formaldehyde, or particles with viruses. The use of air cleaners alone cannot ensure adequate air quality, particularly where significant pollutant sources are present and ventilation is insufficient. See ASHRAE and CDC for more information on air cleaning and filtration and other important engineering controls. 

• See CDC's Interactive School Ventilation Tool to learn how to improve ventilation.

Air Cleaning Devices That Use Bipolar Ionization, Including Portable Air Cleaners and In-duct Air Cleaners Used in HVAC Systems

Some products sold as air cleaners intentionally generate ozone. These products are not safe to use when people are present because ozone can irritate the airways. Do not use ozone generators in occupied spaces . When used at concentrations that do not exceed public health standards, ozone applied to indoor air does not effectively remove viruses, bacteria, mold, or other biological pollutants.

Bipolar ionization (also called needlepoint bipolar ionization) is a technology that can be used in HVAC systems or portable air cleaners to generate positively and negatively charged particles. Provided manufacturers have data to demonstrate efficacy, manufacturers of these types of devices may market this technology to help remove viruses, including SARS-2-CoV, the virus that causes COVID-19, from the air, or to facilitate surface disinfection of surfaces within a treated area. This is an emerging technology, and little research is available that evaluates it outside of lab conditions. As typical of newer technologies, the evidence for safety and effectiveness is less documented than for more established ones, such as filtration. Bipolar ionization has the potential to generate ozone and other potentially harmful by-products indoors, unless specific precautions are taken in the product design and maintenance. If you decide to use a device that incorporates bipolar ionization technology, EPA recommends using a device that meets UL 2998 standard certification (Environmental Claim Validation Procedure (ECVP) for Zero Ozone Emissions from Air Cleaners).

Please note that there are many air cleaning devices that do not use bipolar ionization – the device packaging or marketing materials will typically indicate if bipolar ionization technology is being used.

DIY Air Cleaners

Do-it-yourself (DIY) air cleaners are indoor air cleaners that can be assembled from box fans and square HVAC (or furnace) filters. They are sometimes used during wildfire or other events when air quality is poor and other indoor air filtration options are unavailable.

Evidence from multiple studies indicates that well-built DIY air cleaners can be of comparable effectiveness to commercial air cleaners in reducing airborne particles (including viral particles). However, their performance does vary based on the design selected and the quality of materials and assembly. Each time a DIY air cleaner is re-assembled after changing a filter, its performance may be different. Commercial devices, on the other hand, are tested for performance, and this performance information can be used to match them to the size of a room.

Therefore, EPA does not recommend the routine use of DIY air cleaners as a permanent alternative to products of known performance (such as commercially available portable air cleaners). However, this recommendation should not be interpreted to discourage the use of DIY air cleaners in circumstances when commercially available portable air cleaners or other products of known performance are not available. Using a DIY air cleaner that was inadequately designed or assembled does not worsen indoor air quality and may still offer some benefits.

To address concerns that box fans in DIY air cleaners might be associated with increased risk of fire, EPA and Underwriter Laboratories evaluated the use of DIY air cleaners and the risk of fire. Fans that were built since 2012 and met UL standard 507 did not pose a fire hazard under the conditions tested in the study. (See Research on DIY Air Cleaners to Reduce Wildfire Smoke Indoors for more information.

Tips - If You Choose to Use a DIY Air Cleaner

• Initial costs for single filter designs can be lower than designs that use multiple filters, but operation costs for single filter designs may be higher, for the same performance.
• Multi-filter designs can be harder to put together, and it can be harder to replace their filters. They are also bulkier, and more difficult to move around than single filter designs. However, multi-filter designs generally have superior performance, and they can be more cost effective.
• Using multiple single-filter units in the same room is also worth considering, when balancing performance, costs, space, and ease of assembly for your specific needs.
• Spanish version (pdf)
• One filter flat against the fan (from the Washington Dept of Ecology)
• Two filters taped with cardboard to form a triangle against the fan (from the Confederated Tribes of the Colville Reservation)
• Four filters used to create an air filtration box, also known as the Corsi-Rosenthal box (pdf) (from the University of California, San Diego)
• Use a newer box fan (made since 2012) with a UL (Underwriters Laboratory) or ETL (Intertek) logo because they have verified safety features to reduce the risk of the fan overheating. EPA recommends not using DIY air cleaners built with older model box fans (built before 2012), because their fire hazard is unknown. If older fans are used, they should not be used unattended or while sleeping.
• Use filters of approximately the same shape and size as the box fan. Filters that only partially overlap the fan will result in reduced performance. Filters that are bigger than the fan may be unnecessarily more expensive.
• When assembling a DIY air cleaner, choose a high-efficiency filter, rated MERV 13 or higher, for better filtration. Align the arrows on the filter to be in the same direction of the air flow through the fan. Create a good seal between the fan and the filter.

Features That Can Improve DIY Air Cleaner Performance

• Increase the number of filters in the design. Some designs can have 2, 3, 4 or 5 filters. This feature generally improves performance the most. 
• Use a thick HVAC filter that is 2” or 4” thick instead of a 1” filter. Generally, thicker filters are more expensive than thinner filters, but need to be changed less often. Thicker filters generally provide a large improvement in performance. 
• Cover the outside corners of the front of the box fan  so that air flows only through the center part of the fan where the blades are visible. This approach generally provides a large improvement in performance. You can use cardboard, duct tape, or wood to make the cover – some DIY fan designers call these “shrouds”. This cover can also be made from the cardboard box in which the fan was packaged, at no additional cost. 
• Improve the seal where the filters are attached to the fan or each other. Seal the edges using duct tape, for example, instead of ties or clamps. This is less important for performance than the other features listed above. 

Tips For Operating a DIY Air Cleaner

• Run the device whenever the room is occupied.
• Make sure the device is free from obstructions and air can flow through it.
• Run the device at the highest speed setting acceptable to you.
• Check the filter(s) regularly and replace when dirty.  

Air Cleaner Operation

• Place DIY air cleaners in the rooms where people are spending the most time, in general. To protect especially vulnerable people, place the air cleaner where they spend most of their time.  If someone is isolating because they could be transmitting an infectious disease (such as COVID-19 or flu), place the air cleaner nearest them. 
• Make sure air can flow to the device and away from it, keeping it clear from obstructions. A central place in a room works best, but it is not essential as long as air flow is free. Do not operate an air cleaner inside a closet, as this would limit its effectiveness. 
• Consider running DIY air cleaners the entire time a space is occupied. The longer they run, the more particles they will likely remove.
• Consider running the fan at higher speed settings. Air cleaning performance improves at higher fan speeds, although noise and air movement in the room also increase.
• Change the filters periodically. Longer run times, higher fans speeds, and higher levels of air pollution will mean that the filter will be removing more particles from the air, but the filter will also get dirty more quickly. Change the filter when it appears dirty. When changing the filter(s), wear gloves, an N-95 respirator or similar, and goggles (without holes) for personal protection. Remove the filters gently - outdoors if possible. Avoid shaking or banging the filters to minimize the release of accumulated dust. Dispose of the filters in garbage bags.

Additional Information

• See EPA Air Cleaners and Air Filters in the Home for more information.
• Schools and universities (pdf)  (1.93 MB)
• Commercial buildings (pdf)  (1.32 MB)
• Multifamily owners/managers (pdf) (1.19 MB)
• Core Recommendations for Reducing Airborne Infectious Aerosol Exposure (pdf)  (152.72 KB) 
• Improving Ventilation in Your Home
• CDC Interactive Ventilation Tool (for Homes)

Return to Indoor Air and Coronavirus (COVID-19).

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Climate risk and the opportunity for real estate

Climate change, previously a relatively peripheral concern for many real-estate players, has moved to the top of the agenda. Recently, investors  made net-zero commitments, regulators developed reporting standards, governments passed laws targeting emissions, employees demanded action, and tenants demanded more sustainable buildings. At the same time, the accelerating physical consequences of a changing climate are becoming more pronounced as communities face storms, floods, fires, extreme heat, and other risks.

These changes have brought a sense of urgency to the critical role of real-estate leaders in the climate transition, the period until 2050 during which the world will feel both the physical effects of climate change and the economic, social, and regulatory changes necessary to decarbonize. The climate transition not only creates new responsibilities for real-estate players to both revalue and future-proof their portfolios but also brings opportunities to create fresh sources of value.

The combination of this economic transition and the physical risks of climate change has created a significant risk of mispricing real estate across markets and asset classes. For example, a major North American bank conducted analysis that found dozens of assets in its real-estate portfolio that would likely be exposed to significant devaluations within the next ten years due to factors including increased rates of flooding and job losses due to the climate transition. Additionally, a study of a diversified equity portfolio found that, absent mitigating actions, climate risks could reduce annual returns toward the end of the decade by as much as 40 percent.

Leading real-estate players will figure out which of their assets are mispriced and in what direction and use this insight to inform their investment, asset management, and disposition choices. They will also decarbonize their assets, attracting the trillions of dollars of capital that has been committed to net zero and the thousands of tenants that have made similar commitments. They will then create new revenue sources related to the climate transition.

Building climate intelligence is central to value creation and strategic differentiation in the real-estate industry. But the reverse is also true: real estate is central to global climate change mitigation efforts. Real estate drives approximately 39 percent of total global emissions. Approximately 11 percent of these emissions are generated by manufacturing materials used in buildings (including steel and cement), while the rest is emitted from buildings themselves and by generating the energy that powers buildings. 1 2019 global status report for buildings and construction , International Energy Agency, December 2019.

In addition to the scale of its contribution to total emissions, real estate is critical in global decarbonization efforts for reasons likely to be compelling for investors, tenants, and governments. Significant reductions in emissions associated with real estate can be achieved with positive economics through technologies that already exist. For example, upgrading to more energy-efficient lighting systems and installing better insulation have positive financial returns. Today, newer technologies also make low-carbon heating and cooling systems, such as heat pumps and energy-efficient air conditioning, more cost competitive in many markets and climates. These cost-effective upgrades can create meaningful change while also derisking assets.

We suggest three actions real-estate players can take to thrive throughout the climate transition:

• Incorporate climate change risks into asset and portfolio valuations. This requires building the analytical capabilities to understand both direct and indirect physical and transition risks.
• Decarbonize real-estate assets and portfolios.
• Create new sources of value and revenue streams for investors, tenants, and communities.

Fundamental changes brought on by the climate transition will open new dimensions of competitive differentiation and value creation for real-estate players. More important, leaders will make a valuable contribution to the world’s ability to meet the global climate challenge.

Incorporate climate change risks into asset and portfolio valuations

Climate change’s physical and transition risks touch almost every aspect of a building’s operations and value. Physical risks are hazards caused by a changing climate, including both acute events, such as floods, fires, extreme heat, and storms, and chronic conditions, such as steadily rising sea levels and changing average temperatures. Transition risks include changes in the economy, regulation, consumer behavior, technology, and other human responses to climate change.

We do mind the gap

As we work with real-estate firms, we notice that investment teams increasingly recognize the impact of climate change on asset values. As one leader of valuations at a major real-estate-services firm recently commented to us: “This is the greatest deviation between modeled valuation and actual price that I’ve ever seen, and it’s because of climate.” A chief operating officer of a diversified real-estate investor told us, “We’ve seen underperformance of a cluster of our assets due to climate-related factors that just weren’t considered in our investment theses.”

The industry at large senses how values are shifting. A recent survey of finance experts and professionals conducted by researchers at New York University found that those who think real-estate asset prices reflect climate risks “not enough” outnumber those who think they reflect climate risks “too much” by 67 to 1 (in comparison with stock prices, in which the ratio was 20 to 1). 1 Johannes Stroebel and Jeffrey Wurgler, “What do you think about climate finance?,” Harvard Law School Forum on Corporate Governance, September 3, 2021. The International Renewable Energy Agency has estimated that $7.5 trillion worth of real estate could be “stranded”; these are assets that will experience major write-downs in value given climate risks and the economic transition, making real estate one of the hardest-hit sectors. 2 Jean Eaglesham and Vipal Monga, “Trillions in assets may be left stranded as companies address climate change,” Wall Street Journal , November 20, 2021.

Physical and transition risks can affect assets, such as buildings, directly or indirectly, by having an impact on the markets with which the assets interact. A carbon-intensive building obviously faces regulatory, tenancy, investor, and other risks; over the long term, so does a building that exists in a carbon-intensive ecosystem. For example, a building supplied by a carbon-intensive energy grid or a carbon-intensive transportation system is exposed to the transition risks of those systems as well. All these changes add up to substantial valuation impacts for even diversified portfolios—an increasingly pressing concern for real-estate companies (see sidebar, “We do mind the gap”).

Physical risks, both direct and indirect, have an uneven effect on asset performance

Several major real-estate companies have recently conducted climate stress tests on their portfolios and found a significant impact on portfolio value, with potential losses for some debt portfolios doubling over the next several years. Notably, they found significant variation within the portfolios. Some assets, because of their carbon footprint, location, or tenant composition, would benefit from changes brought on by the climate transition, while others would suffer significant drops in value. The challenge for players is to determine which assets will be affected, in what ways, and how to respond. There is also opportunity for investors who can identify mispriced assets.

Direct physical consequences can be conspicuous: the value of homes in Florida exposed to changing climate-related risks are depressed by roughly $5 billion relative to unexposed homes. According to the Journal of Urban Economics , after Hurricane Sandy, housing prices were reduced by up to 8 percent in New York’s flood zones by 2017, reflecting a greater perception of risk by potential buyers. 2 Francesc Ortega and Süleyman Taspinar, “Rising sea levels and sinking property values: Hurricane Sandy and New York’s housing market,” Journal of Urban Economics , July 2018, Volume 106. In California, there has been a 61 percent annual jump in nonrenewals of insurance (due to higher prices and refused coverage) in areas of moderate-to-very-high fire risk. 3 Elaine Chen and Katherine Chiglinsky, “Many Californians being left without homeowners insurance due to wildfire risk,” Insurance Journal , December 4, 2020.

The indirect impacts of physical risk on assets can be harder to perceive, causing some real-estate players to underestimate them. For example, in 2020, the McKinsey Global Institute modeled expected changes in flooding due to climate change in Bristol, England . A cluster of major corporate headquarters was not directly affected, but the transportation arteries to and from the area were. The water may never enter the lobby of the building, but neither will the tenants.

The climate transition will affect both individual buildings and entire real-estate markets

The investments required to avoid or derisk the worst physical risks will drive a historic reallocation of capital . This will change the structure of our economy and impact the value of the markets, companies, and companies’ locations. These momentous changes require real-estate players to look ahead for regulatory, economic, and social changes that could impact assets.

Among the most direct climate-transition impacts are regulatory requirements to decarbonize buildings, such as New York City’s Local Law 97. In June 2019, the Urban Green Council found that retrofitting all 50,000 buildings covered by the law would create retrofit demand of up to $24.3 billion through 2030. 4 Justin Gerdes, “After pandemic, New York’s buildings face daunting decarbonization mandate,” Greentech Media, April 23, 2020. Standard property valuation models generally do not account for the capital costs required for a building to decarbonize, and investors and operators are often left with a major capital expense or tax that wasn’t considered in the investment memo.

There is also a host of less direct but potentially more significant transition risks that affect whole markets. For example, some carbon-intensive industries are already experiencing rapid declines or fluctuations. In Calgary, for example, the combination of oil price volatility and market-access issues (driven by climate change–related opposition to pipelines) has dramatically depressed revenues from some buildings. Vacancy rates in downtown Calgary reached about 30 percent, a record high, as of January 2021. Investors exposed to the Calgary market have seen their asset values drop precipitously and are left trying to either hold on and hope for a reversal of fortunes or exit the assets and take a significant loss.

Real-estate players should build the capabilities to understand climate-related impacts on asset performance and values

Real-estate owners and investors will need to improve their climate intelligence to understand the potential impact of revenue, operating costs, capital costs, and capitalization rate on assets. This includes developing the analytical capabilities to consistently assess both physical and transition risks. Analyses should encompass both direct effects on assets and indirect effects on the markets, systems, and societies with which assets interact (Exhibit 1).

Portfolio and asset managers can map, quantify, and forecast climate change’s asset value impact

To understand climate change impact on asset values, landlords and investors can develop the following capabilities to understand and quantify risks and opportunities:

• Prioritize. Create a detailed assessment of the asset or portfolio to determine which physical and transition risks are most important and which are less important (using criteria such as the probability of a risk occurring or the severity of that risk).
• Map building exposures. Determine which buildings are exposed to risks, either directly (for example, having to pay a carbon tax on building emissions) or indirectly (for example, exposure to reduction in occupancy as tenants’ industries decline because of a carbon tax), and the degree of exposure (for example, how high floodwaters would reach). This could require detailed modeling of physical hazards (for example, projected changes in flood risks as the climate changes) or macro- or microeconomic modeling (for example, projected GDP impacts based on the carbon price impact on a local geography’s energy production mix).
• Quantify portfolio impact. Combine assessments of the economic risks on individual buildings into an impact map that enables visualization of the entire portfolio (Exhibit 2). This requires combining knowledge of the potential risk or opportunity and an understanding of what drives the economics of a building (including drivers of net operating income, tenancy mix, and areas of cost variability).
• Take action. These capabilities cannot be isolated in a research or environmental, social, and governance (ESG) function but should directly inform investment management, lease pricing, capital attraction and investor relations, asset management, tenant attraction, development, and other core businesses. The processes within organizations must shift to ensure that climate-related insights can be a source of real competitive advantage.

A portfolio revaluation informed by climate change risks can lead to hard choices but will also open the door to acting on decarbonization and exploring new opportunities.

Decarbonize buildings and portfolios

McKinsey research estimates approximately $9.2 trillion in annual investment will be required globally to support the net-zero transition . If the world successfully decarbonizes, the 2050 economy will look fundamentally different from the current economy. If it doesn’t successfully decarbonize, the world will experience mounting physical risks that will strain the foundations of the global economy and society. In either case, the places where people live, work, shop, and play will fundamentally change.

Decarbonizing real estate requires considering a building’s ecosystem

Ultimately, the only way to reduce the risks of climate change is to decarbonize. Real-estate players have a wide array of options for how to proceed, including low-carbon development and construction ; building retrofits to improve energy efficiency; upgrades to heating, cooling, and lighting technology; and technology to manage demand and consumption. But decarbonization is not solely a technical challenge. To develop the most appropriate path, real-estate players need to understand the range of decarbonization options and their financial and strategic costs and benefits.

Decarbonizing real estate

To decarbonize, industry players can take the following steps:

• Understand the starting point. Quantify baseline emissions of each building. This helps real-estate players prioritize where to start (for example, individual buildings, asset classes, or regions) and determine how far there is to go to reach zero emissions.
• Set targets. Decide which type of decarbonization target to set. There is a range of potential target-setting standards that take different approaches (for example, measuring absolute emissions versus emissions intensity, or setting targets at the sector level versus asset level). Players should develop a “house view” on targets that achieve business, investor, stakeholder, regulatory, and other objectives.
• Identify decarbonization levers. Build an asset- or portfolio-level abatement curve. A marginal abatement cost curve  provides a clear view of the potential cost/return on investment of a given emissions-reduction lever along with the impact of that lever on emissions reduction. This approach can be complemented with market and policy scenarios that change the relative costs and benefits of each potential abatement lever.
• Execute. Set up the mechanisms to effectively deploy the decarbonization plan. These may involve making changes to financing and governance, stakeholder engagement (investors, joint-venture partners, operators, and tenants), and a range of operational and risk-management aspects of the business.
• Track and improve. As investors, lenders, and tenants make their own decarbonization commitments, they will need to demonstrate that their real estate is indeed decarbonizing. Thus, much of the value of decarbonizing will come from the ability to demonstrate emissions reduction to potential stakeholders. Building the ability to monitor and progressively reduce emissions on the path to net zero will create an opportunity for players to differentiate.

Create new sources of value and revenue streams for investors, tenants, and communities

As the economy decarbonizes, real-estate players can use their locations, connections to utility systems, local operational footprints, and climate intelligence to create new revenue streams, improve asset values, or launch entirely new businesses.

Opportunities include the following:

• Local energy generation and storage. Real-estate firms can use their physical presence to generate and store energy. For example, property developers have been outfitting buildings with solar arrays and batteries, helping to stabilize energy grids and reduce the costs associated with clean energy. 5 “5 ways clean tech is making commercial RE more energy efficient,” Jones Lang LaSalle, April 20, 2021.
• Green buildings to attract more tenants. Developers and property managers can invest in developing green buildings or retrofitting older buildings to make them green to meet the growing appetite for sustainable workplaces and homes.
• Green-building materials. Players can explore the advantages of green steel, tall timber, modular construction, and other emerging technologies and materials that may have additional benefits, such as faster and lower-cost construction.
• Extra services on-site. Firms can introduce new revenue streams, including vehicle charging, green-facilities management, and other on-site services that enable occupants’ sustainable preferences.
• Services for reducing and tracking emissions. Firms can support occupants by tracking emissions and offering solutions to reduce carbon footprints. These services could include smart sensors and tracking energy consumption through heating, cooling, lighting, and space management.
• Differentiated capital attraction. Given the volume of capital that has already been committed to achieving net zero, firms that are able to decarbonize will have an advantage in attracting capital. Real-estate players may, for example, create specific funds for net-zero buildings or investment themes that support community-scale decarbonization.

The coming climate transition will create seismic shifts in the real-estate industry, changing tenants’ and investors’ demands, the value of individual assets, and the fundamental approaches to developing and operating real estate. Smart players will get ahead of these changes and build climate intelligence early by understanding the implications for asset values, finding opportunities to decarbonize, and creating opportunity through supporting the transition.

Real estate not only will play a critical role in determining whether the world successfully decarbonizes but also will continue to reinvent the way we live, work, and play through these profound physical and economic changes.

This article was edited by Katy McLaughlin, a senior editor in the southern California office.

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Related articles.

Call for action: Seizing the decarbonization opportunity in construction

Glasgow COP26 2021: Decarbonizing the built environment

Virtual 2021: Sustainability in the construction ecosystem

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• National Institutes of Health NIH
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Dietary Supplements for Immune Function and Infectious Diseases

This is a general overview. For more in-depth information, see our health professional fact sheet .

How does your immune system work?

Your immune system is made up of cells , tissues , and organs that help fight viruses , bacteria , and other germs that cause infections and other diseases. For example, your skin helps prevent germs from getting inside your body. Cells that line your digestive tract also help protect against harmful germs that cause diseases. White blood cells try to destroy substances they recognize as foreign to your body. Some white blood cells also recognize germs they have been exposed to before and develop antibodies to defend against them in the future.

What do we know about specific dietary supplement ingredients and immune function?

Your immune system needs certain vitamins and minerals to work properly. These include vitamin C , vitamin D , and zinc . Herbal supplements , probiotics, and other dietary supplement ingredients might also affect your immune system.

Eating a variety of nutritious foods can give you enough vitamins, minerals, and other nutrients for a healthy immune system. However, you might wonder whether taking certain dietary supplements can improve your body’s immune system and its ability to fight infections.

This fact sheet describes what we know about the effectiveness and safety of common vitamins, minerals, and other dietary supplement ingredients that might affect immune function .

Dietary supplement ingredients are presented in each section in alphabetical order.

The health professional version of this fact sheet includes more details and references to the scientific literature .

Vitamins and Minerals

Getting enough vitamins and minerals through the foods and beverages you consume is important for a healthy immune system. It’s especially important to get enough of vitamins A, B6, B12, C, D, E, and K as well as folate , copper , iodine , iron , magnesium , selenium , and zinc.

If your diet doesn’t include adequate amounts of certain vitamins and minerals, your immune system will not be able to function as well as it could, you might be more likely to get infections, and you might not recover as well. If your health care provider determines that you are not getting enough of a specific nutrient, vitamin and mineral supplements can help increase intakes to recommended amounts. In most cases, however, if you don’t have a deficiency , increasing your intake of vitamins and minerals through dietary supplements doesn’t help prevent infections or help you recover from them any faster.

Vitamin A is an essential nutrient found in many foods. It exists in two different forms:

• Preformed vitamin A is found in fish, organ meats (such as liver ), dairy products, and eggs.
• Provitamin A carotenoids are turned into vitamin A by your body. They are found in fruits, vegetables, and other plant-based products. The most common provitamin A carotenoid in foods and dietary supplements is beta-carotene .

Vitamin A is important for healthy immune function as well as vision, reproduction, growth, and development.

Vitamin A deficiency is rare in the United States, but it is common in many low- and middle-income countries.

The recommended daily amount (known as Recommended Dietary Allowance or RDA) ranges from 300 to 1,200 microgram (mcg) retinol activity equivalents (RAE) for infants , children, and teens, depending on age, and from 700 to 1,300 mcg RAE for adults.

Does it work?

Diarrhea in children.

Children with a vitamin A deficiency are more likely to get diarrhea caused by germs. These children also have a higher chance of dying of diarrhea, especially in sub-Saharan Africa and south Asia.

Research suggests that vitamin A supplements lower the risk and severity of diarrhea in children in low- and middle-income countries. However, vitamin A supplementation might not help very young infants in these countries.

HIV infection

HIV infection can decrease your appetite and weaken your body’s ability to use nutrients from food. HIV can also increase the risk of related health problems, such as diarrhea and respiratory diseases.

It’s not clear if vitamin A supplements lower the risk of spreading HIV or keep the disease from getting worse. Some studies in young children with HIV have found that vitamin A supplements help lower the risk of death. However, it’s not clear whether vitamin A supplements affect the risk of diarrhea or respiratory infections in young children with HIV. Other studies in adults with HIV have found that vitamin A supplements do not improve immune function.

Research in pregnant people with HIV has found that vitamin A supplements do not help reduce the chance of passing HIV from mother to infant. However, one study found that pregnant people with HIV who took vitamin A were more likely to carry their babies to full-term.

Measles in children

In low- and middle-income countries where vitamin A deficiency is common, children with measles are more likely to have severe symptoms and may die from the disease. In these children, vitamin A supplements might help prevent measles, but it’s unclear whether they lower the risk of dying from measles.

Pneumonia and other respiratory infections in children

Is it safe.

Preformed vitamin A is safe at daily intakes up to 600 to 2,800 mcg for infants, children, and teens, depending on age, and up to 3,000 mcg for adults. There are no upper limits for beta-carotene and other forms of provitamin A.

Getting too much preformed vitamin A can cause severe headache, blurred vision, nausea , dizziness, muscle aches, and problems with coordination. In severe cases, getting too much preformed vitamin A can even lead to coma and death.

If you are pregnant, taking too much preformed vitamin A can cause birth defects, including abnormal eyes, skull, lungs , and heart. If you are or might be pregnant or breastfeeding, you should not take high-dose supplements of preformed vitamin A.

High intakes of beta-carotene (provitamin A) do not cause the same problems as preformed vitamin A. Consuming high amounts of beta-carotene can turn the skin yellow-orange, but this condition is harmless and goes away when you eat less of it. However, several studies have shown that smokers, former smokers, and people exposed to asbestos who take high-dose beta-carotene supplements have a higher risk of lung cancer and death.

Vitamin A supplements might interact with some medications such as orlistat (used for weight loss), acitretin (used to treat psoriasis ), and bexarotene (used to treat the skin effects of T-cell lymphoma ).

More information about vitamin A is available in the ODS consumer fact sheet on vitamin A .

Vitamin C is an essential nutrient found in citrus fruits and many other fruits and vegetables. Vitamin C is an antioxidant and is important for healthy immune function. The body also needs vitamin C to make collagen .

The RDA ranges from 15 to 115 milligrams (mg) for infants, children, and teens, depending on age, and from 75 to 120 mg for nonsmoking adults. People who smoke need 35 mg more than the RDA per day.

Common cold

Taking vitamin C regularly might help decrease cold symptoms and reduce the number of days a cold lasts. It might also help reduce the risk of getting a cold in people who undergo extreme physical stress, such as marathon runners and soldiers stationed in very cold locations. However, taking vitamin C after coming down with a cold may not be helpful.

Research suggests that vitamin C supplements might be more effective in people who do not get enough vitamin C from foods and beverages.

Sepsis (using intravenous vitamin C, not vitamin C supplements)

Sepsis is a life-threatening complication of an infection that can damage the body’s organs and tissues. It’s not clear whether high-dose intravenous (IV) vitamin C helps treat sepsis, and in some cases it might be harmful. In some studies, IV vitamin C reduced the risk of death, but in other studies it did not affect the risk of death or the amount of organ damage. Other research suggests that IV vitamin C might increase the risk of death or organ damage.

Vitamin C is safe at daily intakes up to 400 to 1,800 mg for children and teens, depending on age, and up to 2,000 mg for adults. Taking higher amounts of vitamin C can cause diarrhea, nausea, and stomach cramps, and it might also cause false readings on blood sugar monitors, which are used by people with diabetes . In people with hemochromatosis (an iron overload disorder ), high amounts of vitamin C might cause iron build-up in the body, which can damage body tissues.

Vitamin C supplements might decrease the effectiveness of radiation therapy and chemotherapy .

More information about vitamin C is available in the ODS consumer fact sheet on vitamin C .

For information about vitamin C and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Vitamin D is an essential nutrient that is naturally present in fatty fish and fish liver oils and in small amounts in beef liver, egg yolks, and cheese. It’s also added to some foods, such as fortified milk. Your body can also make vitamin D when your skin is exposed to the sun. Vitamin D is important for healthy bones and immune function.

The RDA ranges from 10 to 15 mcg (400 International Units [ IU ] to 600 IU) for infants, children, and teens, depending on age, and from 15 to 20 mcg (600 to 800 IU) for adults.

Flu, pneumonia, and other respiratory infections

People with low vitamin D levels might be more likely to get respiratory infections and might have a higher chance of dying from these infections. Some studies suggest that taking vitamin D supplements regularly might slightly reduce the risk of getting a respiratory infection, especially in people with low vitamin D levels. However, other studies have not found that taking vitamin D supplements reduces the risk of respiratory infections. In addition, vitamin D supplements do not appear to help treat respiratory infections.

People with HIV have a higher risk of vitamin D deficiency partly because many HIV medications cause the body to break down vitamin D faster than normal. Having a vitamin D deficiency might also worsen HIV infection. However, studies haven’t shown that vitamin D supplements improve the health of people with HIV.

Vitamin D is safe at daily intakes up to 25 to 100 mcg (1,000 to 4,000 IU) for infants, children, and teens, depending on age, and up to 100 mcg (4,000 IU) for adults. Taking higher amounts can cause nausea, vomiting, muscle weakness, confusion, pain, loss of appetite, dehydration, excessive urination and thirst, and kidney stones . Extremely high doses can cause kidney failure , damaged blood vessels and heart valves, heart rhythm problems, and death.

Vitamin D supplements might interact with some medications such as orlistat (used for weight loss), statins (used to lower cholesterol levels), thiazide diuretics (used for high blood pressure ), and steroids.

More information about vitamin D is available in the ODS consumer fact sheet on vitamin D .

For information about vitamin D and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Vitamin E (also called alpha-tocopherol ) is an essential nutrient found in nuts, seeds, vegetable oils, and green leafy vegetables. It acts as an antioxidant and helps your immune system function properly. Vitamin E deficiency is rare.

The RDA is 4 to 15 mg for infants, children, and teens, depending on age, and 15 to 19 mg for adults.

Pneumonia and other respiratory infections

It’s not clear whether vitamin E supplements reduce the risk or severity of respiratory infections. Some studies have found that vitamin E supplements might help but others have not, and the effects might depend on whether someone has low vitamin E levels. One study in people who had normal vitamin E levels found that those who took high-dose vitamin E supplements had worse respiratory symptoms and were sick longer.

Vitamin E from food is safe at any level. In supplements, vitamin E is safe at daily intakes up to 200 to 800 mg for children and teens, depending on age, and up to 1,000 mg for adults. Taking higher amounts can increase the risk of bleeding and stroke .

Vitamin E supplements might interact with blood thinners and might reduce the effectiveness of radiation therapy and chemotherapy.

More information about vitamin E is available in the ODS consumer fact sheet on vitamin E .

For information about vitamin E and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Selenium is an essential mineral found in many foods, including Brazil nuts, seafood, meat, poultry , eggs, dairy products, bread, cereals, and other grain products. It acts as an antioxidant and is important for reproduction, thyroid gland function, and DNA production.

The RDA ranges from 15 to 70 micrograms (mcg) for infants, children, and teens, depending on age, and from 55 to 70 mcg for adults.

People with HIV have higher risk of selenium deficiency than other people, and this might worsen their infection and increase the risk of death. However, it’s not clear whether taking selenium supplements improves the health of people with HIV. Some studies have found that selenium supplements might improve immune function slightly in people with HIV, but other studies have not.

Selenium is safe at daily intakes up to 45 to 400 mcg for infants, children, and teens, depending on age, and up to 400 mcg for adults. Taking higher amounts can cause a garlic odor in the breath, a metallic taste in the mouth, hair and nail loss or brittleness, skin rash, nausea, diarrhea, fatigue , irritability, and nervous system problems.

Selenium might interact with cisplatin (a drug used in chemotherapy).

More information about selenium is available in the ODS consumer fact sheet on selenium .

For information about selenium and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Zinc is an essential nutrient found in seafood, meat, beans, nuts, whole grains , and dairy products. It’s important for a healthy immune system, making proteins and DNA, healing wounds, and for proper sense of taste.

The RDA ranges from 2 to 13 mg for infants, children, and teens, depending on age, and from 8 to 12 mg for adults.

Some studies suggest that zinc lozenges and zinc syrup speed recovery from the common cold if you start taking them at the start of a cold. However, these products don’t seem to affect the severity of cold symptoms. More research is needed to determine the best dose and form of zinc for the common cold as well as how often and how long it should be taken.

Pneumonia in children

Some studies in lower income countries show that zinc supplements lower the risk of pneumonia in young children. However, zinc doesn’t seem to speed recovery or reduce the number of deaths from pneumonia.

Studies show that zinc supplements help shorten the duration of diarrhea in children in low-income countries, where zinc deficiency is common. The World Health Organization and UNICEF recommend that children with diarrhea take zinc for 10 to 14 days (20 mg/day, or 10 mg/day for infants under 6 months). However, it’s not clear if zinc supplements help children with diarrhea who already get enough zinc, such as most children in the United States.

Many people with HIV have low zinc levels. This occurs because they have trouble absorbing zinc from food and they often have diarrhea, which increases zinc loss. Some studies have found that supplemental zinc decreases diarrhea and complications of HIV, but other studies have not. Zinc supplements do not appear to reduce the risk of death in people with HIV.

Zinc is safe at daily intakes up to 4 to 34 mg for infants, children, and teens, depending on age, and up to 40 mg for adults. Taking higher amounts can cause nausea, vomiting, loss of appetite, stomach cramps, diarrhea, and headaches. High intakes of zinc over a long time can cause low blood levels of copper and impair immune function.

Zinc supplements might interact with antibiotics , penicillamine (used to treat rheumatoid arthritis ), and thiazide diuretics (used to treat high blood pressure).

More information about zinc is available in the ODS consumer fact sheet on zinc .

For information about zinc and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Andrographis

Andrographis is an herb native to Southeast Asia. It might help your body fight viruses, reduce inflammation , and strengthen your immune system.

Common cold and other respiratory infections

Some studies have found that taking andrographis after getting a cold or other respiratory infection might lessen the severity of symptoms and shorten the length of time symptoms last. However, additional studies are needed to confirm these findings.

No safety concerns have been reported when andrographis is used as directed. Side effects of andrographis can include nausea, vomiting, dizziness, skin rashes, diarrhea, and fatigue.

Andrographis might decrease blood pressure and thin the blood, so it could interact with blood pressure and blood thinning medications.

Andrographis might also decrease the effectiveness of medications that suppress the immune system. Andrographis might affect fertility, so some scientists recommend avoiding it if you are pregnant or planning to have a baby.

For information about andrographis and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Echinacea is an herb that grows in North America and Europe. It might help stop the growth or spread of some types of viruses and other germs. It might also help strengthen your immune system and reduce inflammation.

Common cold and flu

Studies have found that echinacea might slightly reduce the risk of catching a cold, but it doesn’t reduce the severity of symptoms or shorten the length of time symptoms last.

It’s unclear whether echinacea is helpful for the flu.

Echinacea appears to be safe. Side effects can include stomach upset, diarrhea, trouble sleeping, and skin rashes. In rare cases, echinacea might cause allergic reactions.

Echinacea might reduce the effectiveness of some medications, including medications that suppress the immune system. Scientists don’t know if echinacea is safe to take during pregnancy.

For information about echinacea and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Elderberry (European Elder)

Elderberry (or elder berry) is the fruit of a tree that grows in North America, Europe, and parts of Africa and Asia. Elderberry might help your body fight viruses and other germs, reduce inflammation, and strengthen your immune system.

Elderberry doesn’t appear to reduce the risk of coming down with the common cold. However, some studies have found that elderberry might help relieve symptoms of colds and flu and help people recover quicker.

Elderberry flowers and ripe fruit appear to be safe to eat. However, the bark, leaves, seeds, and raw or unripe elderberry fruit can be poisonous and can cause nausea, vomiting, diarrhea, and dehydration. Cooked elderberry fruit and properly manufactured supplements do not have this safety concern.

Elderberry might affect insulin and blood sugar levels. It might also reduce the effectiveness of medications that suppress the immune system. Scientists don’t know if elderberry is safe to take during pregnancy.

For information about elderberry and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Garlic is a vegetable that has been used in cooking throughout history . It is also available as a dietary supplement.

Garlic might help your body fight viruses and other germs.

Only a few studies have looked at whether garlic supplements help prevent the common cold or flu, and it’s not clear if garlic is helpful.

Garlic is considered safe. Side effects can include bad breath, body odor, and skin rash.

Garlic might interact with blood thinners and blood pressure medications.

Ginseng ( Panax ginseng or Panax quinquefolius ) is a plant used in traditional Chinese medicine. It might help your body fight viruses, reduce inflammation, and strengthen your immune system.

Another botanical , eleuthero ( Eleutherococus senticosus ), has sometimes been called Siberian ginseng, but it is not related to true ginseng.

Common cold, flu, and other respiratory infections

Ginseng might reduce the risk of coming down with the common cold, flu, or other respiratory infections. However, it’s unclear whether ginseng helps relieve symptoms or affects the length of time symptoms last.

Ginseng appears to be safe. Side effects can include headache, trouble sleeping, and digestive upset. However, high doses (more than 2.5 grams [g]/day) of ginseng might cause insomnia , rapid heartbeat, high blood pressure, and nervousness.

Ginseng might interact with diabetes medications, stimulants , and medications that suppress the immune system.

For information about ginseng and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Tea and tea catechins

Tea ( Camellia sinensis ) is a popular beverage that may have health benefits. Tea extracts are also available as dietary supplements.

Green, black, and oolong tea leaves are processed in different ways. Green tea is made from dried and steamed tea leaves, and black and oolong teas are made from fermented tea leaves.

Tea, especially green tea, has high amounts of substances called catechins. Catechins might help fight viruses and other germs.

Flu and other respiratory infections

Based on only a few studies, it’s unclear whether tea or tea catechins are helpful for the flu or other respiratory infections. Some studies have found that tea and tea catechins might reduce the risk of coming down with upper respiratory infections. They might also reduce the length and severity of some symptoms but not other symptoms.

Tea is safe to drink. Side effects of green tea extract can include nausea, constipation , stomach discomfort, and increased blood pressure. Some green tea extracts might damage your liver, especially if you take them on an empty stomach.

Tea also contains caffeine, which can disturb your sleep and cause nervousness, jitteriness, and shakiness. Safe doses of caffeine for healthy adults are up to 400 to 500 mg/day and up to 200 mg/day for people who are pregnant.

Tea might interact with atorvastatin (a cholesterol-lowering drug) and stimulants, such as bitter orange or ephedrine.

Other Ingredients

Glutamine is an amino acid found in many foods including beef, fish, poultry, dried beans, eggs, rice, grains, and dairy products. Your body makes enough glutamine to meet your needs, except under rare conditions (for example, if you are critically ill in an intensive care unit [ICU] or have had major surgery).

Glutamine helps your immune system work properly.

Critical illness (giving glutamine as an IV or tube feeding)

It’s unclear whether glutamine helps people who are critically ill. Some studies in hospitalized patients who were critically ill or had undergone major surgery found that glutamine given as an IV or tube feeding reduced the risk of getting an infection, but it did not reduce the risk of death.

Glutamine is considered safe. Side effects can include nausea, bloating, burping, pain, gas, and vomiting. These side effects are more likely to occur with higher doses of glutamine.

No interactions between glutamine and medications have been reported.

N-acetylcysteine and glutathione

N-acetylcysteine (NAC) is similar to cysteine, an amino acid. It acts as an antioxidant and helps reduce mucus in the respiratory tract .

NAC raises levels in your body of a substance called glutathione, which also acts as an antioxidant. NAC and glutathione might also help your body fight viruses and other germs, reduce inflammation, and strengthen your immune system.

People with HIV may have low levels of glutathione, which might increase the risk of certain diseases including tuberculosis . However, there is very little research on NAC supplements in people with HIV. Therefore, scientists don’t know whether it’s helpful.

NAC appears to be safe. Side effects can include nausea, vomiting, stomach pain, diarrhea, indigestion, and heartburn.

NAC might interact with blood thinners and blood pressure medications. Taking NAC with nitroglycerine (used to treat chest pain) might cause low blood pressure and severe headaches.

For information about NAC and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Omega-3 fatty acids

Omega-3s are types of fats, including alpha linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is found mainly in plant oils, such as flaxseed, soybean , and canola oils. EPA and DHA are found mainly in fatty fish and fish oils.

Omega-3s are important for healthy cell membranes and proper function of the heart, lungs, brain, immune system, and endocrine system .

The recommended amount of omega-3s for infants is 0.5 g per day, and 0.7 to 1.6 g per day of ALA for children, teens, and adults, depending on age. EPA and DHA do not have individual recommendations.

Omega-3s might help your body fight viruses and other germs, reduce inflammation, and strengthen your immune system.

Acute respiratory distress syndrome (giving omega-3s as an IV or tube feeding)

Acute respiratory distress syndrome (ARDS) is a serious lung condition that can lead to death. In people who do recover, ARDS often causes long-term physical and mental health problems.

Researchers have studied whether giving omega-3s as an IV or tube feeding is helpful for people with ARDS, but results from these studies are not clear. Some studies have found that omega-3s given in this manner might help the lungs work better, but they don’t appear to lower the risk of dying from ARDS. In addition, it’s not clear whether omega-3s given in this manner affect the length of time people are hospitalized with ARDS and need a ventilator to help them breathe.

Respiratory infections in infants and young children

The immune system continues to develop in babies after birth, and their immune cells contain the omega-3s EPA and DHA. However, it’s not clear whether adding omega-3s to infant formula improves immune function or reduces the risk of getting respiratory infections.

A study in school-age children found that children who consumed milk with added EPA and DHA had fewer upper respiratory infections than those who did not consume omega-3s. In another study, however, using an infant formula containing DHA and another fatty acid had no effect on the risk of respiratory infections in infants.

Omega-3s are considered safe. Side effects can include a bad taste in the mouth, bad breath, heartburn, nausea, digestive discomfort, diarrhea, headache, and smelly sweat. Omega-3s might interact with blood thinners, blood pressure medications, and medications that suppress the immune system.

More information about omega-3s is available in the ODS consumer fact sheet on omega-3 fatty acids .

For information about omega-3s and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Probiotics are live microorganisms (bacteria and yeasts) that provide health benefits. They are naturally present in certain fermented foods, added to some food products, and available as dietary supplements. Probiotics act mostly in the stomach and intestines . They might improve immune function and help fight viruses.

Acute diarrhea in infants and children

Acute infectious diarrhea in infants and children causes loose or liquid stools and three or more bowel movements within 24 hours. This condition is often caused by a viral infection and can last for up to a week. Some infants and children also develop fever and vomiting. Some studies have shown that probiotics shorten acute diarrhea by about 1 day, but other studies do not.

Some studies have reported that two strains of probiotics— Lactobacillus rhamnosus GG (LGG) and Saccharomyces boulardii —were most likely to benefit children with acute infectious diarrhea, but other studies have not.

Probiotics might reduce the risk of some respiratory infections and shorten the length of illness. Some studies in infants, children, and adults have found that probiotics reduce the risk of getting a cold and help relieve some symptoms, such as fever and cough. Other studies in children reported fewer sick days from school and quicker recovery. However, formulations of probiotics vary, and the effects of one product may not be the same as another.

Ventilator-associated pneumonia

It’s not clear whether probiotics help people who are critically ill. Some studies have found that probiotics lower the risk of developing pneumonia in people who are critically ill and need a ventilator to help them breathe, but other studies have not.

Probiotics are considered safe for most people. Side effects can include gas and other digestive symptoms. In people who are very ill or have immune system problems, probiotics might cause severe illness. Probiotics might also cause infections or even life-threatening illness in preterm infants. Although probiotics don’t appear to interact with medications, taking antibiotics or antifungal medications might decrease the effectiveness of some probiotics.

More information about probiotics is available in the ODS consumer fact sheet on probiotics .

For information about probiotics and COVID-19, see the ODS consumer fact sheet, Dietary Supplements in the Time of COVID-19 .

Do dietary supplements interact with medications or other supplements?

Yes, some supplements can interact or interfere with medicines you take.

Tell your doctor, pharmacist , and other health care providers about any dietary supplements and prescription or over-the-counter medicines you take. They can tell you if the dietary supplements might interact with your medicines or if the medicines might interfere with how your body absorbs , uses, or breaks down nutrients.

Where can I find out more about dietary supplements and immune function?

• Office of Dietary Supplements (ODS) Health Professional Fact Sheet on Dietary Supplements for Immune Function and Infectious Diseases

• Herbs at a Glance , National Center for Complementary and Integrative Health
• ODS Frequently Asked Questions: Which brand(s) of dietary supplements should I purchase?

This fact sheet by the National Institutes of Health (NIH) Office of Dietary Supplements (ODS) provides information that should not take the place of medical advice. We encourage you to talk to your health care providers (doctor, registered dietitian, pharmacist, etc.) about your interest in, questions about, or use of dietary supplements and what may be best for your overall health. Any mention in this publication of a specific brand name is not an endorsement of the product.

Updated: November 14, 2023

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Plants can communicate and respond to touch. Does that mean they're intelligent?

Tonya Mosley

"The primary way plants communicate with each other is through a language, so to speak, of chemical gasses," journalist Zoë Schlanger says. Mohd Rasfan/AFP via Getty Images hide caption

"The primary way plants communicate with each other is through a language, so to speak, of chemical gasses," journalist Zoë Schlanger says.

In the 1960s and '70s, a series of questionable experiments claimed to prove that plants could behave like humans, that they had feelings, responded to music and could even take a polygraph test .

Though most of those claims have since been debunked, climate journalist Zoë Schlanger says a new wave of research suggests that plants are indeed "intelligent" in complex ways that challenge our understanding of agency and consciousness.

"Agency is this effect of having ... an active stake in the outcome of your life," Schlanger says. "And when I was looking at plants and speaking to botanists, it became very clear to me that plants have this."

In her new book, The Light Eaters: How the Unseen World of Plant Intelligence Offers a New Understanding of Life on Earth , Schlanger, a staff reporter at The Atlantic, writes about how plants use information from the environment, and from the past, to make "choices" for the future.

Happy Arbor Day! These 20 books will change the way you think about trees

Schlanger notes that some tomato plants, when being eaten by caterpillars, fill their leaves with a chemical that makes them so unappetizing that the caterpillars start eating each other instead. Corn plants have been known to sample the saliva of predator caterpillars — and then use that information to emit a chemical to attract a parasitic wasp that will attack the caterpillar.

Stop overwatering your houseplants, and other things plant experts want you to know

Schlanger acknowledges that our understanding of plants is still developing — as are the definitions of "intelligence" and "consciousness." "Science is there [for] observation and to experiment, but it can't answer questions about this ineffable, squishy concept of intelligence and consciousness," she says.

But, she adds, "part of me feels like it almost doesn't matter, because what we see plants doing — what we now understand they can do — simply brings them into this realm of alert, active processing beings, which is a huge step from how many of us were raised to view them, which is more like ornaments in our world or this decorative backdrop for our our lives."

Interview highlights

On the concept of plant "intelligence"

Intelligence is this thing that's loaded with so much human meaning. It's too muddled up sometimes with academic notions of intelligence. ... Is this even something we want to layer on to plants? And that's something that I hear a lot of plant scientists talk about. They recognize more than anyone that plants are not little humans. They don't want their subjects to be reduced in a way to human tropes or human standards of either of those things.

On the debate over if plants have nervous systems

I was able to go to a lab in Wisconsin where there [were] plants that had ... been engineered to glow, but only to glow when they've been touched. So I used tweezers to pinch a plant on its vein, ... the kind of mid-rib of a leaf. And I got to watch this glowing green signal emanate from the point where I pinch the plant out to the whole rest of the plant. Within two minutes, the whole plant had received a signal of my touch, of my "assault," so to speak, with these tweezers. And research like that is leading people within the plant sciences, but also people who work on neurobiology in people to question whether or not it's time to expand the notion of a nervous system.

On if plants feel pain

TED Radio Hour

Plants don't have brains — but they sure act smart.

We have nothing at the moment to suggest that plants feel pain, but do they sense being touched, or sense being eaten, and respond with a flurry of defensive chemicals that suggest that they really want to prevent whatever's going on from continuing? Absolutely. So this is where we get into tricky territory. Do we ascribe human concepts like pain ... to a plant, even though it has no brain? And we can't ask it if it feels pain. We have not found pain receptors in a plant. But then again, I mean, the devil's advocate view here is that we only found the mechanoreceptors for pain in humans, like, fairly recently. But we do know plants are receiving inputs all the time. They know when a caterpillar is chewing on them, and they will respond with aggressive defensiveness. They will do wild things to keep that caterpillar from destroying them further.

On how plants communicate with each other

Zoë Schlanger is a staff writer at The Atlantic. Heather Sten/Harper Collins hide caption

Zoë Schlanger is a staff writer at The Atlantic.

The primary way plants communicate with each other is through a language, so to speak, of chemical gasses. ... And there's little pores on plants that are microscopic. And under the microscope, they look like little fish lips. ... And they open to release these gasses. And those gasses contain information. So when a plant is being eaten or knocked over by an animal or hit by wind too hard, it will release an alarm call that other plants in the area can pick up on. And this alarm call can travel pretty long distances, and the plants that receive it will prime their immune systems and their defense systems to be ready for this invasion, for this group of chewing animals before they even arrive. So it's a way of saving themselves, and it makes evolutionary sense. If you're a plant, you don't want to be standing out in a field alone, so to speak. It's not good for reproductive fitness. It's not good for attracting pollinators. It's often in the interest of plants to warn their neighbors of attacks like this.

On plant "memory"

Research News

Orangutan in the wild applied medicinal plant to heal its own injury, biologists say.

There's one concept that I think is very beautiful, called the "memory of winter." And that's this thing where many plants, most of our fruit trees, for example, have to have the "memory," so to speak, of a certain number of days of cold in the winter in order to bloom in the spring. It's not enough that the warm weather comes. They have to get this profound cold period as well, which means to some extent they're counting. They're counting the elapsed days of cold and then the elapsed days of warmth to make sure they're also not necessarily emerging in a freak warm spell in February. This does sometimes happen, of course. We hear stories about farmers losing their crops to freak warm spells. But there is evidence to suggest there's parts of plants physiology that helps them record this information. But much like in people, we don't quite know the substrate of that memory. We can't quite locate where or how it's possibly being recorded.

On not anthropomorphizing plants

What's interesting is that scientists and botany journals will do somersaults to avoid using human language for plants. And I totally get why. But when you go meet them in their labs, they are willing to anthropomorphize the heck out of their study subjects. They'll say things like, "Oh, the plants hate when I do that." Or, "They really like this when I do this or they like this treatment." I once heard a scientist talk about, "We're going to go torture the plant again." So they're perfectly willing to do that in private. And the reason for that is not because they're holding some secret about how plants are actually just little humans. It's that they've already resolved that complexity in their mind. They trust themselves to not be reducing their subjects to human, simplistic human tropes. And that's going to be a task for all of us to somehow come to that place.

It's a real challenge for me. So much of what I was learning while doing research for this book was super intangible. You can't see a plant communicating, you can't watch a plant priming its immune system or manipulating an insect. A lot of these things are happening in invisible ways. ... Now when I go into a park, I feel totally surrounded by little aliens. I know that there is immense plant drama happening all over the place around me.

Sam Briger and Susan Nyakundi produced and edited this interview for broadcast. Bridget Bentz and Molly Seavy-Nesper adapted it for the web.

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• Open access
• Published: 09 May 2024

Identification of the needs of individuals affected by COVID-19

• Halina B. Stanley   ORCID: orcid.org/0000-0001-6043-4669 1 ,
• Veronica Pereda-Campos   ORCID: orcid.org/0000-0002-7365-6217 2 ,
• Marylou Mantel 1 , 2 ,
• Catherine Rouby 1 ,
• Christelle Daudé   ORCID: orcid.org/0000-0001-7368-2557 1 ,
• Pierre-Emmanuel Aguera   ORCID: orcid.org/0000-0001-5765-5196 1 ,
• Lesly Fornoni 1 ,
• Thomas Hummel   ORCID: orcid.org/0000-0001-9713-0183 3 ,
• Susanne Weise   ORCID: orcid.org/0000-0001-7650-1731 3 ,
• Coralie Mignot 3 ,
• Iordanis Konstantinidis 4 ,
• Konstantinos Garefis   ORCID: orcid.org/0000-0003-3905-5650 4 ,
• Camille Ferdenzi   ORCID: orcid.org/0000-0001-5572-0361 1 ,
• Denis Pierron 2 &
• Moustafa Bensafi   ORCID: orcid.org/0000-0002-2991-3036 1  

Communications Medicine volume  4 , Article number:  83 ( 2024 ) Cite this article

23 Accesses

Metrics details

• Lifestyle modification
• Olfactory system

The optimal management of COVID-19 symptoms and their sequelae remains an important area of clinical research. Policy makers have little scientific data regarding the effects on the daily life of affected individuals and the identification of their needs. Such data are needed to inform effective care policy.

We studied 639 people with COVID-19 resident in France via an online questionnaire. They reported their symptoms, effects on daily life, and resulting needs, with particular focus on olfaction.

The results indicate that a majority of participants viewed their symptoms as disabling, with symptoms affecting their physical and mental health, social and professional lives. 60% of the individuals reported having unmet medical, psychological and socio-professional support needs. Finally, affected individuals were concerned about the risk and invasiveness of possible treatments as shown by a preference for non-invasive intervention over surgery to cure anosmia.

Conclusions

It is important that policy makers take these needs into consideration in order to assist affected individuals to regain a normal quality of life.

Plain Language Summary

The impact of COVID-19 has been substantial, both on individuals’ health and on society. Information is needed to understand the biological mechanisms underlying the illness and to provide appropriate support for people affected. This study uses data from an online questionnaire of adults diagnosed with COVID-19 to characterize symptoms, understand their impact on peoples’ everyday lives, and determine the support that people need. Our over-arching analysis of symptoms experienced reveals that heart- and skin-related symptoms are linked to chronic illness, and symptoms related to the sense of smell may have a different underlying disease mechanism. Most respondents had a mild initial illness, but their symptoms were long-lasting and had a severe impact. Our findings show that sufferers need different kinds of support in order to regain a normal quality of life.

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Introduction.

By end-January 2023 there have been over 670 million cases of COVID-19 worldwide 1 and the consequences of the COVID-19 crisis continue to emerge. Estimates of the incidence of long-term sequelae vary widely, but numbers are significant, of the order of at least 3% of those infected 2 , 3 , 4 , 5 , 6 with long-term effects for perhaps 50–85% of those hospitalized 7 , 8 , 9 .

It is known that COVID-19 is associated with a large spectrum of symptoms ranging from the classic symptoms of flu, through gastro-intestinal, cardiac and renal, cognitive and olfactory and gustatory dysfunctions 10 , 11 , 12 , 13 , 14 . Three years after the start of the pandemic data are now emerging on long-lasting symptoms and sequelae even for patients with apparently mild initial illness 2 , 10 , 15 and theoretical studies are underway to understand the mechanisms underlying the appearance of symptoms, such as molecular level investigations of infected cells 16 , 17 , the role of inflammation 18 and potential drivers of long-COVID 19 .

Nevertheless, fundamental data remain incomplete and sometimes contradictory. COVID-19 is a multi-organ heterogeneous disease with many interacting factors: age, sex, comorbidities. Scientific knowledge is needed to help clinicians improve their diagnoses ( https://www.who.int/teams/blueprint/covid-19 ) and also to help improve patients’ health by developing better adapted treatment strategies 20 , 21 , 22 .

Although studies are underway (e.g. ref. 23 ) characterization of COVID-19 symptoms (whether persistent or not) and their effect on quality of life, as well as identifying patients’ needs, has not yet been conducted with the level of detail that would allow a clear analysis of the situation.

To date, several questions remain regarding COVID-19 symptoms: how do they differ from one person—or group of persons—to another? What are their dynamics of appearance? How are they associated with each other? What differences are there between the acute and chronic phases? There is also a lack of actionable data on the impact these symptoms have on the quality of life of those affected. Are all these symptoms disabling? How do they affect psychological health? Dietary health? Social life and relationships? Working life? And above all, what are the needs of those affected in terms of medical, psychological and socio-professional support?

Today, policy makers and stakeholders have little scientific data on which to base an effective policy for caring for those affected and to define the resources needed (in terms of financial support, social services or care) to meet their needs, and to plan for future pandemics. If spending can be targeted effectively this could mitigate overall increases in health spending over the medium to long term 24 . The main aim of the present study is to provide characterization of a wide range of symptoms of COVID-19, their effects on quality of life and the needs of those affected. To achieve this goal, we conducted an online study involving a large sample of participants affected by symptoms several days, weeks or months after infection 25 . In this survey, we documented the presence of symptoms by category (flu-like, gastro-intestinal, cognitive & neurological, cutaneous & inflammatory, cardiac & renal, olfactory/gustatory, other), their onset and persistence, their effects on people’s daily lives and also identified people’s needs regarding these symptoms. In addition, to understand how inter-individual factors such as age and gender might explain the diversity in symptoms, effects on quality of life, and patients’ needs, we conducted systematic analyses for each of these three areas.

As a secondary aim, we explored the question of olfactory/gustatory loss in more detail, as this symptom affects several million people worldwide, a quarter to a third of whom continue to have some degree of measurable smell dysfunction for months after their infection 26 , 27 , 28 and emerging information on a possible link between these COVID-19 olfactory symptoms and dementia is concerning 22 . Moreover, in addition to serious psychological and social effects 29 , 30 , 31 , anosmia (total loss of smell) and parosmia (distorted perception of smell) symptoms exacerbate the malnutrition documented post-COVID 32 , 33 . Finally, we collected verbatim responses in order to capture individual experiences and enrich our quantitative analysis.

We find a high prevalence of chronic symptoms, concerning a higher proportion of women than men. Olfactory, gustatory and flu-like symptoms were frequently experienced early in the illness, with cutaneous, inflammatory and cardiac symptoms often delayed. The data also show the severe impact flu-like and cognitive symptoms have on people’s everyday lives. We confirm the dietary impact of olfactory symptoms on sufferers and provide a detailed overview of the interventions desired by those affected by the long-term effects.

Selection of the participants

There were a total of 1054 responses in the study. However, we limited the analysis to adults (over 18 years old), resident in France, who were answering the questionnaire for the first time and completed the entire survey which left us 751 participants. We wanted to ensure, as much as reasonably possible, that symptoms arose from COVID-19 infection so only included participants diagnosed COVID+ either by an analytical test (PCR, lateral flow, blood test etc.) or by a doctor on the basis of their symptoms alone. This excluded 36 self-diagnosed participants and 55 participants without COVID-19. We also excluded 5 participants who did not record the date of their diagnosis, 3 participants who gave an implausible date (prior to the first diagnoses in France on the 24th January 2020 1 , 34 and 13 participants who recorded a diagnosis date after their recovery date (see Fig.  1 ), ending with a final sample of 639 participants.

751 people completed the whole survey who were over 18 years old, resident in France and completing the survey for the first time. Of these, 55 people who had no diagnosis and 36 people who were self-diagnosed were excluded. A further 21 participants were then excluded owing to implausible or missing diagnosis dates.

It should be noted that our analysis does not focus specifically on the “long COVID-19” population, although many participants fall into this category. This survey focused on the symptoms and needs of patients who have had COVID-19 infection, regardless of any subjective persistence of symptoms. Moreover, one can consider oneself cured of COVID-19, but still experience long-term sequelae and express needs. Thus, our analyses include all people who have been infected by Sars-Cov-2, whether they declare themselves cured or not.

Experimental protocol

The descriptive cohort study was conducted between 15th July 2021 and 6th September 2022. It was approved by the Institutional Review Board of INSERM (IRB00003888, IORG0003254, FWA00005831) of the French Institute of medical research and health, under number 21-805. The study consisted of a cross-sectional online participatory survey. Participants had access to the questionnaire on the website https://project.crnl.fr/covid/ . They learned about the survey through their internet searches and we also distributed the link to our scientific and academic network, and to the communication officers of the French institutions involved in the project. The first page of the website mentioned the objectives of the study and several pieces of information concerning the average time of completion and the way in which the answers are taken into account. It was also stated that the questionnaire is anonymous and that the record of their responses to the questionnaire does not contain any identifying information. Once this information was read, the participant was asked to provide their consent to participate in the survey. Afterwards, the participant was asked to answer several questions specifying: their age, gender, weight, height, socio-professional category, education level, place of residence, pregnancy (if female), smoking habits, if he/she has any chronic diseases and treatment, information about COVID-19 (diagnosis, hospitalization, treatment, vaccination), type and duration of symptoms (early, persistent), influence of these symptoms on psychological well-being, diet, social life, professional life, needs for medical follow-up, psychological follow-up, socio-professional follow-up and other needs and therapies. The details of the survey are given in  Supplementary Notes   1 .

Characteristics of the sample of COVID-19+ patients surveyed

The principal characteristics of the survey participants are provided in Table  1 . The people were mostly of working age (75th percentile is 52 years) and predominantly (77%) female. The majority experienced mild initial illness. Only 42 people were hospitalized (7%), of whom 25 received oxygen and 8 were treated in intensive care. 110 people (17%) were either occasional or regular smokers, which compares to 18.5% of people over 18 years old in France 35 . Further demographic information (on age and gender distribution, BMI, smoking habits, pregnancy status, participants’ illness & medication, vaccination status, hospitalization, temporal information on dates of diagnostic and survey completion) is detailed in  Supplementary Notes   2 . There were no significant gender related differences in the age distributions.

The diagnosis dates range from the beginning of the pandemic (30th January 2020) to 29th August 2022 and correlate well with the waves of infection in France over this time 25 . The average number of days between a positive COVID diagnosis and completing the survey is 281 (see Supplementary Fig.  11 ). 54 of the 639 respondents completed the questionnaire less than two weeks after their COVID+ diagnosis.

Note that the diagnosis dates cover waves of infection with different dominant variants, with an under-representation of the delta & omicron variants (see ref. 25 ). However, we do not have sufficient confirmed diagnoses of the variant of infection (this was an open question) for us to be able to perform a statistical analysis comparing the different variants.

There is good geographical representation across metropolitan France, with a bias towards the Lyon, Toulouse and Paris areas. We have some over-representation of urban areas ( Supplementary Notes   3 ).

Data analysis

The data were extracted from the survey using the open-source software package Jamovi 36 , 37 which was also used to extract some of the figures and all statistical tests.

We used descriptive statistics tools (percentage and 95% confidence intervals) to define the prevalence and dynamics of symptom appearance, to evaluate the disabling effect of symptoms on quality of life, and to identify the needs arising from all symptoms and to perform the in-depth analysis of specific needs for olfactory losses.

Generally, percentages were calculated relative to (i) the whole survey population (ii) the whole survey population by gender (iii) number reporting different symptom categories and (iv) number reporting presence of symptom by gender (note that the single individual who did not define their gender was excluded from all gender-based analyses).

Furthermore, 95% confidence intervals were calculated using the Effect Sizes and Confidence Intervals add-on module for Jamovi (esci) which uses the recommended method of Newcombe and Altman 38 (The code for this is available on github, lines 118–127 for a single proportion and lines 456–474 for the difference of two proportions https://github.com/rcalinjageman/esci/blob/master/R/estimateProportions.R ).

P values for significance were calculated using jamovi with 2 sided tests for both proportions (for categorical data using χ 2 and the z test for the difference in 2 proportions) and averages (for continuous data assuming equal variances). These are reported without corrections for multiple comparisons.

Finally, Pearson correlation coefficients r between different symptom categories were calculated by binarising the categorical data, mapping lack of symptom to zero and symptom experienced to one.

Reporting summary

Further information on research design is available in the  Nature Portfolio Reporting Summary linked to this article.

Here we first quantify the prevalence of the different symptoms for our survey population, together with the dynamics of onset & recovery and also examine symptom associations. We then examine responses related to the impact that these symptoms had on people’s everyday lives and the needs people expressed. We provide an in-depth analysis for olfactory loss.

Supplementary Notes   4 provides detailed information on the effect of gender and age differences on the prevalence of symptoms and their dynamics of onset and recovery.  Supplementary Notes   5 provides detailed information for the subjects’ perception of their illness by symptom category, its disabling nature and their associated needs. Selected verbatim responses on the impact of each symptom, together with their translations into English, are also provided

Characterization of the symptoms experienced

Prevalence of symptoms.

Amongst our survey participants, 65% had olfactory/gustatory symptoms [95% CI 61–69%], 92% had flu-like symptoms [95% CI 90–94%], 66% [95% CI 62–70%] had cognitive, neurological or psychiatric, 56% [95% CI 52–60%] had gastro-intestinal symptoms, 38% [95% CI 34–42%] had cardiac or renal symptoms and 37% [95% CI 33–40%] had skin or inflammatory symptoms (see Fig.  2a ). 33% [95% CI 29–37%] of people reported “other” symptoms. Responses for “other” symptoms were free and we note that symptoms were sometimes included here that could have been included elsewhere. People frequently mentioned extreme fatigue, breathlessness and cognitive symptoms such as tinnitus, vertigo, anxiety & headaches. Several people had issues with their eyesight or eyes. Women experienced menstrual changes and one man testicular pain. Some mentioned hair loss, pain in articulations, or reactivation of other viruses such as herpes simplex. Overall, 628 participants (98%) experienced at least one symptom and 55 participants (8.6%) experienced all the symptoms.

a Proportion of survey participants reporting symptoms by symptom category. Error bars are 95% confidence intervals. Inset in bars: Number of survey participants and percentage of survey population. b Proportion of survey participants by symptom onset (symptoms began in first month (yellow); later (gray)). Inset in bars: Number of survey participants and percentage by symptom category experienced. c Symptom associations. Upset plot illustrating the number of participants reporting different combinations of symptoms. The largest number of people (74) only experienced flu-like and olfactory symptoms.

Regarding gender and age, women were more likely to experience symptoms than men in all symptom categories ( p  < 0.001). The average age of those reporting symptoms was higher than for those not reporting symptoms, except for olfactory/gustatory symptoms where there was no significant difference (Supplementary Fig.  17 ).

Dynamics of appearance of symptoms

Most participants experienced loss of olfaction and gustation, and flu-like symptoms within the first month of infection, however onset of cognitive, cutaneous & inflammatory, cardiac & renal symptoms was frequently delayed (see Fig.  2b ). There were no significant gender or age differences for the onset of symptoms (Supplementary Figs.  18 and   19 ).

Associations between symptoms

Figure  2c depicts the number of participants reporting different combinations of symptoms. The largest subset of people (11.6%) had only flu-like and olfactory/gustatory symptoms, and while 27 people only had flu-like symptoms, 15 had only olfactory/gustatory symptoms. We also note that 14% of the survey population suffered all symptoms, or all symptoms except “other” (that are not well defined). 139 people (21.8% of the survey population) reported flu-like and cardiac and cognitive and cutaneous and gastro-intestinal symptoms. We found that the incidence of these symptoms was correlated, but that there was no correlation, or an anti-correlation, with olfactory/gustatory symptoms (Fig.  3 ).

Pearson’s r factor calculated from binary vectors, p  < 0.05 interpreted as correlated, p  < 0.01 very correlated. The heatbar corresponds to the Pearson r coefficients. The number of subjects experiencing each symptom category given in Fig.  2 .

Persistence of symptoms

Overall, only 31% (200) of the 639 participants reported recovery at the time of completing the survey, with younger people and men more likely to report recovery than older people and women ( Supplementary Notes   4 ). The median number of days between diagnosis and recovery (for the 200 people reporting recovery) was 18 (range 0–462). 439 people (69%) did not report recovery. However, 47 of these 439 people completed the survey less than 15 days after their diagnosis (when symptoms are to be expected) and 57 of the 439 people responded within 5 weeks. There were 363 people (57%) who did not report recovery more than 3 months after diagnosis. Only 53 people in our sample reported recovery after more than 35 days, and for 33 of these people it took between three and fifteen months after diagnosis.

For gender and age, more women than men reported persistent flu-like and gastro-intestinal symptoms ( p  < 0.001 and p  = 0.004 respectively). The average age of those reporting persistent symptoms was higher than those without persistent symptoms for all symptom categories except gastro-intestinal and cutaneous & inflammatory symptoms ( Supplementary Notes   4 ).

Disabling effect of symptoms and impact on daily life

Disabling effect of symptoms.

A large proportion of survey participants found their symptoms a handicap in their everyday life (see Fig.  4a ). Overall 75% of participants who reported olfactory loss found it handicapped them, 72% of those with gustatory loss, 81% of those with flu-like symptoms (which included headaches, fatigue and weakness), 63% of those with gastro-intestinal symptoms, who struggled with nausea and diarrhea, 90% of those with cognitive symptoms (mentioning depression, “brain fog”, memory and concentration problems) and 81% of those with cardiac or renal symptoms (who suffered tachycardia and chest pain among other symptoms) (see  Supplementary Notes   5 and Supplementary Notes   6 for Selected verbatim responses on the impact of each symptom). More women than men found their flu-like, gastro-intestinal, cutaneous & inflammatory, and cardiac & renal symptoms handicapped them in their everyday life, but there was no gender difference for olfactory/gustatory and cognitive symptoms. There were no age-related differences in the perception of whether any of these symptoms were handicapping in everyday life.

a Percentage of people finding their symptoms handicapping (orange) or not (green) by symptom category. b Reported impact of symptoms on psychological health (blue), diet (orange), social & relational life (gray) and professional life (yellow) as a proportion of those experiencing each symptom category. The number of participants concerned is reported inside the bar.

Impact on daily life

Suffering any of the symptoms had an impact on the psychological health of over a third of respondents, rising to 70% of those with flu-like symptoms and 83% of those with cognitive symptoms (see Fig.  4b ). Diet was affected for 50% or more of participants with olfactory, gustatory, flu-like or gastro-intestinal symptoms. Diet was also affected by cognitive, neurological and psychiatric type symptoms for over a third of people and by cardiac or renal symptoms for over a quarter of sufferers. Respondents’ social and professional lives were impacted for over two thirds of those with flu-like, cognitive, cardiac or renal symptoms. Regarding gender, although persistently more women than men reported impacts on their everyday lives this was rarely statistically significant. The small number of men concerned in many of these comparisons make conclusions on this unreliable (see  Supplementary Notes   5 ). The only significant age-related difference was for flu-like symptoms, which younger people found affected their professional life more than older people (average ages 42.8 [41.8,43.9] years and 46.5 [43.0,50.0] years for those finding their flu-like symptoms affected their professional life or didn’t, respectively) (see  Supplementary Notes   5 ).

Identification of needs

Needs by type of symptoms. Overall, 60% of the survey population (382 people) expressed a need for some kind of help with managing their symptoms (see Fig.  5a ), with a higher proportion of women than men ( p  = 0.002) (see  Supplementary Notes   5 ). The average age of those seeking additional help was higher than the average age of those with no needs ( p  < 0.001) (see  Supplementary Notes   5 ). There was no significant gender difference, or difference in the average age, between the group who reported that they had sufficient help with their symptoms already, and the group who reported they needed additional assistance ( p  = 0.155).

a Overall, 60% of the participants stated that they had needs that were not being addressed. Percentages are relative to the total survey population. N(no symptoms):11; N(no help needed):161; N(needs taken care of):85; N(help needed):382. b Overview of stated needs by symptom experienced. Proportions as a percentage of those experiencing each symptom. Specialist medical help required (dark blue), specialist psychological help required (light blue), socio-professional assistance required (gray).

Of those that expressed a need for additional follow-up help, the majority, 58% (371 participants) wanted specialist medical help, 25% (158 participants) wanted help from a psychologist or psychiatrist, and 21% (137 participants) wanted socio-professional help.

Unsurprisingly, for those experiencing cognitive, neurological and psychiatric symptoms (migraines, forgetfulness, attention deficits, speech problems, confusion, anxiety, depression, sleep disorders etc.) there was also a significant desire for psychological and socio-professional support (see Fig.  5b ). These people frequently cited an inability to work (see  Supplementary Notes   5 ).

The majority of the participants who reported that they had not yet recovered from their symptoms stated that they needed help, and only a small proportion said they had sufficient help already. Specifically, confining ourselves to participants who reported that they had not yet recovered from their symptoms, the percentage of people needing help was: 66% of people with olfactory symptoms, 69% of people with gustatory symptoms, 87% of people with flu-like symptoms, 73% of people with gastro-intestinal symptoms, 84% of people with cognitive symptoms, 73% of people with cutaneous symptoms, 89% of people with cardiac symptoms and 88% of people with “other” symptoms (see Fig.  6 ).

Gray: no help needed; red: I have needs that are not met; blue: I have needs for which I have sufficient help. The number of participants concerned is provided inside the bars.

Detailed analysis for a specific symptom: olfactory loss

We conducted a detailed investigation for olfactory losses. Of the 416 survey participants reporting olfactory and/or gustatory loss, 389 (94%) experienced loss of olfaction and 80% (332) reported loss of sense of taste (see Fig.  7a, b ). Of the participants losing olfaction 295 (76%) reported a total loss. This olfactory loss was frequently associated with changed odors (parosmia) (55%) and phantom odors (42%). These changed and phantom odors were almost invariably unpleasant with participants describing them as putrefaction, drains, sweat, burning, cigarette smoke, rotten eggs etc.

a Proportion of the 639 survey participants reporting loss of olfaction. b Proportion with loss of gustation. c Acceptable treatments for olfactory loss as a proportion of the survey population experiencing olfactory loss. Error bars are calculated 95% confidence intervals. Inset in bars: Number of participants and percentage of those with olfactory loss.

Of the individuals losing gustation 209 (63%) reported a total loss. This gustatory loss was associated with changed tastes in 63% of the participants and phantom tastes in 23% of the cases. People had difficulty describing their changed and phantom tastes; although many described metallic, burnt or rotten tastes, some said that food had a taste of perfume or “carrot juice tastes of flowers”. One person said everything tasted like toothpaste and another that courgette soup tasted of fish. Note that 10 of the 416 participants reporting olfactory and/or gustatory symptoms reported no loss of smell or of taste. It is unclear whether these participants experienced changed or phantom symptoms as if a participant did not report loss these questions were not asked. Two thirds of the participants with olfactory and/or gustatory symptoms provided verbatim comments, reflecting a high degree of distress amongst this population (see  Supplementary Notes   5 ).

Survey participants reporting olfactory loss were also asked what potential interventions they would accept to restore their sense of smell. 73% (283 participants) would follow olfactory training over several months, 31% (122 participants) would choose a new medical treatment over several months, nearly a quarter were prepared to wear a non-invasive olfactory prosthesis and 12% (47 people) would accept nasal surgery. 10 people indicated acceptance of a prosthesis requiring invasive brain surgery (see Fig.  7c ).

The objective of the present study was to characterize the symptoms and sequelae of COVID reported by affected individuals, as well as the impact that these symptoms have on their quality of life. In particular, our study aimed to identify the needs of the persons concerned in terms of medical, psychological and socio-professional support.

In terms of prevalence, we found that although over 93% of the people in our survey were not hospitalized, the proportion of people with symptoms was high (see Fig.  2a ) and only 31% (200/639) reported recovery. We expect our data to suffer from self-selection bias so extrapolation of the prevalence of symptoms from our data to the general population cannot be rigorous, however the numbers of people concerned are high. The prevalence of different symptoms of COVID varies very widely in the literature 11 , 22 , 39 , 40 , 41 , 42 , 43 , 44 , 45 . Early in the pandemic reports were centered on symptoms experienced by those with more severe illness and may not reflect the statistics of the large population with milder initial illness. Prevalence also appears to vary with COVID-19 variant and in particular with the onset of the omicron variant. For example 46 , states that 52.7% of people experienced anosmia during the delta variant wave compared to only 16.7% during the omicron wave (for comparison we find 61% reporting olfactory loss with data mostly prior to the omicron wave). The estimates of the prevalence of asymptomatic cases also vary widely 47 , 48 , 49 with vaccination also playing a role 50 ; however this population is clearly under-represented in our data. Finally, the onset of cognitive, cardiac and cutaneous symptoms is frequently delayed so the prevalence of these symptoms may be under-reported in studies of acute illness.

Moreover, gender effects and age differences were observed. For gender, the women in our study were significantly more likely than men to have symptoms and took longer to recover. For age, we find that the average age of those reporting gastro-intestinal, cardiac, cutaneous or cognitive symptoms was greater than that of those without these symptoms. However, olfactory/gustatory symptoms have a different patient profile to these symptom categories since there was no statistical difference in the average age of those suffering olfactory and gustatory symptoms and those not ( p  = 0.164) (consistent with the results of Stankevice et al. 51 ). Nevertheless, the average age of those with persistent olfactory loss ( p  = 0.013) was higher than that of those without, agreeing with the results of Makaronidis et al. 52 .

Regarding the dynamics of appearance of the symptoms, participants in our survey reported the early onset of olfactory/gustatory, flu-like and gastro-intestinal symptoms, agreeing with Kaye et al., Lechien et al. 53 , 54 and Groff et al. 55 but cognitive and cardiac/renal symptoms frequently began after the first month agreeing with Jason et al. and Davis et al. 56 , 57 . We find that the appearance of cutaneous and inflammatory symptoms is often delayed, although the work of Polly and Fernandez 58 indicates that these conditions are heterogeneous. Davis et al. 59 also made these global observations. Davis et al. and Apple et al. 57 , 60 associated the delayed onset of neurological symptoms with younger people, but we find no statistically significant difference in age for this factor ( p  = 0.470). We also found no dependence on age for the onset of cardiac/renal symptoms ( p  = 0.356) but there was a tendency for those experiencing cutaneous symptoms in the first month to be younger than those with a later onset ( p  = 0.069). One question raised by these data is why different symptom categories have different onset dynamics. It is tempting to associate early onset symptoms (loss of smell, flu) with direct upper respiratory infection and the persistent cognitive impairment, late onset cardiac problems and skin lesions, alopecia, etc. with an immune response to the virus, perhaps with delayed effects over time. This hypothesis, which is rather speculative, deserves to be tested with an interdisciplinary approach combining neuro-sensory, medical and biological research via a longitudinal patient follow-up study.

Finally, regarding associations between symptoms, the literature often focuses on individual symptoms, but our study suggests that a broader analysis may reveal interesting patterns. First, we showed that almost all symptoms were correlated with each other. However, whilst olfactory and gustatory disorders were highly correlated with each other, these two types of disorders were not correlated with any other category of symptoms, suggesting different mechanisms underlying their genesis. We also found that there was a strong correlation (Pearson’s r = 0.51) between cardiac and cutaneous symptoms, and that those with symptoms in these categories were likely to have multiple symptoms and chronic disease. Finally, of those surveyed, the largest subgroup suffered only from flu and olfactory/gustatory symptoms, with the second largest group suffering from all categories of symptoms. To summarize, the symptomatology of COVID-19 should not be seen in a unidimensional way but through a pattern of symptoms that may be more or less prevalent and associated with each other, and with a specific appearance dynamic.

Although all symptom categories were classed as “handicapping” for a significant number of sufferers our data show that some are more disabling than others. For example, cognitive disorders (P(Yes) = 90% [87%, 93%]) are reported to be more disabling than skin disorders (50% [44%, 57%]) (see Fig.  4a ). Furthermore, each type of symptom does not affect people’s quality of life in the same way. While smell disorders have a great impact on diet (62%) and psychological health (55%), cognitive disorders affect people’s professional life (79%) as well as their psychological health (83%), social and relational life (75%), with diet less affected (35%) (see Fig.  4b ).

Overall, 60% of the participants declared that they needed support of various kinds, with only 25% declaring that they did not need support (and 13% that their needs were already taken care of). This inter-individual difference may be related to difficulties in accessing health care systems (e.g. distance, personal and financial resources etc.), a feeling of vulnerability to the disease that differs from one person to another, or the fact of being affected by very disabling symptoms. However, we find a substantial healthcare burden, which even may be under-estimated: time will tell. Of those still suffering cardiac/renal symptoms at the time of completing the survey only 11% said they had no need of help; the numbers for cutaneous, cognitive, gastro-intestinal, flu-like and “other” were 26%, 16%, 26%, 13% and 12% respectively.

The symptom categories with highest needs were flu-like (with participants reporting headaches, fatigue, muscle and joint pain) and cognitive (migraines, forgetfulness, lack of attention, anxiety, sleep disorders etc.) as these symptoms concerned the highest number of participants, but all symptom categories were problematic. Cognitive disorders (e.g., difficulty in concentrating or with memory) affect social activities and leave people unable to work 59 ; participants were also impacted by sleep disorders. Selected verbatim responses can be found in  Supplementary Notes   6 .

The free responses to our survey also highlight the severe disruption to daily life that olfactory loss can produce 61 , 62 , 63 , 64 , 65 , 66 . Anosmia significantly affects the hedonic perception of food, reducing people’s desire to prepare and eat food, which causes weight gain, weight loss and nutritional deficits 29 . Epidemiological studies link nutrition with psychological wellbeing 67 , 68 , 69 and anosmia with depression 70 , 71 and generally reduced emotional well-being 72 , 73 . COVID-19 associated olfactory loss is not very different from other post-viral olfactory loss in terms of quality of life 74 . Although roughly a third of people with olfactory or gustatory symptoms said they needed no help, of those wanting help and still experiencing symptoms only 14.2% (21/148) and 11.5% (13/113) respectively said their needs were met (see Fig.  6 ). It is concerning that for people resident in France, which has an excellent healthcare system 75 , most need is not met.

In our study we also set out to evaluate the technologies that people affected by anosmia were willing to accept as treatment. We found that olfactory training was the most acceptable method (70%), probably because it was considered less invasive, less expensive and less risky. On the other hand, brain surgery was rarely selected as an option (although 3% of people said they would accept it). It is interesting that 24% of the participants considered the use of a non-invasive prosthesis a possible treatment. A non-invasive olfactory prosthesis is probably considered a less risky treatment than brain surgery, the latter being possibly associated in people’s minds with unfounded efficacy in olfaction, risks and uncertainties and a longer recovery time 76 , 77 . The similar acceptability of medication and non-invasive prostheses is interesting, however the well-known disconnect between intention and action means that this result needs corroboration 78 .

To summarize, despite the fact that over 93% of our survey population initially had a relatively mild illness, without a need for hospitalization, symptoms were found to be long-lasting and to have a severe impact. People reported dietary problems, pain and inability to work and predominantly requested medical intervention. Over all symptom categories, we note that medical support is sought nearly two to three times more than psychological and/or socio-professional support. Medical support is important in managing the evolution of immediate and severe persistent symptoms and can also help manage co-morbidities. However, although only 20% of the people requested psychological or socio-professional follow-up, it is important not to discount this need, as we may hypothesize that participants did not choose this option owing to embarrassment 79 , or other response bias. In future work it would be interesting to determine if the need for psychological support is linked to the duration of the symptoms or to people’s uncertainty as to their evolution. We note that verbatim comments we have collected show that persistent symptoms affect the ability of people to lead a normal social and professional life, and we link this to the requests for socio-professional support. We believe that the economic aspect is also an important parameter to be considered and would like to see future work examining the impact of a potential reduction in affected persons’ working hours or even loss of employment. It is possible that the need for psychological or work-related support is under-estimated, or may increase over time. Finally, the focus on the needs of people who have lost their sense of smell also provides information on an important dimension: the notion of risk and invasiveness. These two notions are clearly integrated in people’s choices and it is important for researchers and policy makers to take these concerns into account when research projects or governmental measures related to these needs are, or will be, put in place.

Although our study has provided interesting insights into the symptoms and impact of COVID, we note that, in common with any random survey, our data are limited to those people who chose to respond and to complete a long questionnaire. Our survey population has a preponderance of women and a large number of people with “long COVID” (this appears typical for this kind of survey, for example the online survey of Davis et al. 59 contained 78.7% women and for >91% of the people recovery time exceeded 35 weeks. The survey of Ferdenzi et al. 65 had a gender bias of 78% women and that of Bousquet et al. 66 82% women). We also over-represent urban, educated individuals and exclude those with no internet access. These are selection biases for which no good statistical correction can be made (e.g. ref. 80 ). We can assume a selection bias towards people motivated to seek assistance with symptoms that are problematic for them. There is also the possibility that people who chose to respond are especially health sensitive. The large proportion of the survey population needing help with their symptoms may not, therefore, be reflected in the general population. Moreover, our data are entirely subjective with no external analytical control. We appreciate that we are collecting subjective information based on people’s individual perceptions and that these perceptions may be different for different populations or change with time; nevertheless such “expressed need” is fundamental information for policy makers to take into account.

Our selection criteria exclude self-diagnosed individuals. It is possible that self-diagnosed people may have additional barriers towards accessing care compared to those with a diagnosis of COVID-19. On the other hand, we do include individuals diagnosed COVID+ on the basis of their symptoms alone. This is necessary given the limited testing available at the beginning of the pandemic, but we may include people whose symptoms are not caused by COVID-19. Generally in terms of symptoms we rely on self-assessment with no external analytical control. For example, it is known that people are relatively poor at evaluating their olfactory and gustatory deficits; people often believe they have a deficit when objective testing shows that they are normal, or conversely remain unaware of their real deficits 64 . It may also be the case that people did not correctly identify gustatory loss, as people often confuse this with olfactory loss 81 , 82 although recent work 83 did confirm loss of taste associated with COVID-19 using the “GCCR Smell and Taste check” test (see also ref. 27 ). A further limitation is that “Other” symptoms are not defined. At the end of the survey participants were simply asked to describe symptoms that they had not mentioned in preceding questions. Some participants included symptoms, such as breathlessness and fatigue (which had been listed in the previous description of “Flu-like symptoms”) or anxiety (which had been listed under “cognitive symptoms”). The symptoms described as “other” are very heterogeneous.

Finally, although as commented above, the prevalence of symptoms varies with COVID-19 variant (e.g. ref. 46 ) we do not have a large enough sample size to be able to evaluate this factor.

Nevertheless, taken as a whole, our data do have features that give confidence in the information provided. They show that the average age of hospitalized people is greater than that of un-hospitalized people and that the average age of those with symptoms is higher than the average age of those without, correlating with known information relating to the vulnerability of people to COVID-19 increasing with age. The greater vulnerability of women towards developing chronic effects (which is what we implicitly measure via self-selection bias) is also consistent with recent studies 5 , 84 . The dates reported by the participants are consistent with the different waves of infection in France 85 . Finally the geographical distribution of the participants correlates well with official government indicators 86 , 87 .

Another result that needs to be discussed is that a significant proportion of participants declared themselves cured of COVID-19, yet later described a number of persistent symptoms (80/200). These responses, which at first sight seem counterintuitive, are undoubtedly linked to the fact that declaring oneself cured of COVID-19 depends in part on subjective factors, on the individual perception of each person. This individual perception, which our data show to be variable from one person to another, is possibly constructed on the basis of the appreciation of the severity of the persistent symptoms, or of the feeling that people have still not recovered their initial state of health. In fact, all of this suggests that there is no simple definition of who is considered cured or not cured.

The participants in our study experienced a relatively mild initial illness, but were nevertheless highly symptomatic with a large number finding their symptoms handicapping. The presence of symptoms of different types was correlated, with the notable exception of those of olfactory/gustatory nature, which appear to have a different patient profile. Flu-like and olfactory/gustatory symptoms invariably began early in the illness, but for many people cognitive, cutaneous & inflammatory, and cardiac symptoms began after the first month. Women were significantly more likely than men to have symptoms and a higher proportion of women than men reported they needed additional help. In terms of age, the average age of those with symptoms (of all types except olfactory/gustatory) was higher than that of those without and the average age of those seeking additional help was higher than the average age of those with no needs.

Our study shows symptoms severely affect both physical and mental health together with social and professional interactions. We highlight here the often neglected impact of olfactory loss on sufferers’ nutrition, mood, safety & social interactions, for these people improved access to olfactory training is needed, as few medical solutions exist. It is important that policy makers act to enable affected people regain a normal quality of life. Multidisciplinary support is needed to help manage the physical, emotional and social challenges of the disease: people predominantly ask for specialist medical help, for which improved access is needed, but patients with anxiety & depression need help managing their mental health and those unable to work normally need adequate financial support and help with managing their professional challenges. There is also a need for raising awareness in the general population by fighting against fake news, supporting scientific research, and supporting caregivers and families.

Finally, the magnitude of the health burden suggested by this study is of concern, but the true impact in the general population remains uncertain. The inherent selection biases of an online survey may overestimate, or underestimate, the problem. To extrapolate to the general population, we need results from random representative samples, data which are hard to obtain given the heterogeneous nature of the disease and (ideally) the need for clinical examinations. Nevertheless, given the scale of the problem already emerging, we feel this should be a priority.

Data availability

The source data used for all analysis described here has been deposited on the open access database zenodo in csv format 88 together with a text readme file, a pdf with the survey questionnaire and three descriptive json files. We also provide a description of these data 89 .

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Acknowledgements

This Project has received funding from both the European Union’s Horizon 2020 research and innovation programme under grant agreement No 964529 (Pathfinder Rose project) and the Human Chemosensation IRP project granted by the CNRS.

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Conceived, designed the study: V.P.C., M.M., D.P., M.B.; Data acquisition and curation: H.B.S., C.D., P.E.A., L.F., M.B.; Data organization: M.B. and H.B.S.; Performed analysis: H.B.S.; Wrote the first draft of the paper: H.B.S. and M.B.; Edited and approved the final manuscript: H.B.S., V.P.C., M.M., C.R., C.D., P.E.A., L.F., T.H., S.W., C.M., I.K., K.G., C.F., D.P., M.B.

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Stanley, H.B., Pereda-Campos, V., Mantel, M. et al. Identification of the needs of individuals affected by COVID-19. Commun Med 4 , 83 (2024). https://doi.org/10.1038/s43856-024-00510-1

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Received : 30 May 2023

Accepted : 25 April 2024

Published : 09 May 2024

DOI : https://doi.org/10.1038/s43856-024-00510-1

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