The latest on long COVID
What we know (and what we still don't know).
- Reviewed by Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
While the COVID pandemic has largely faded into the background, one aspect of the virus continues to linger: long COVID. Long COVID is defined as the continuation or development of new symptoms at least three months after the initial infection from SARS-CoV-2 (the virus that causes COVID) without any other explanation. Long COVID affects an estimated 6% to 11% of adults who have had COVID, according to the most recent statistics from the CDC, and scientists continue to learn more about how it affects people and its possible long-term effects. To help answer some of the more common questions about long COVID, we turned to Dr. Michael VanElzakker, a neuroscientist and long COVID researcher at Harvard-affiliated Massachusetts General Hospital.
Q. How much do we know about long COVID?
Dr. VanElzakker: We know quite a bit and there are some good leads on what may be driving symptoms. However, the research is challenging to sort through for two main reasons. One is that COVID is a new phenomenon, so we don't have many long-term studies. The second main research challenge is that "long COVID" is a broad catch-all label that includes any new symptoms that continued or developed after an initial SARS-CoV-2 infection. For some people, this could mean unusually profound fatigue or trouble concentrating, but it can also mean shortness of breath, loss of taste or smell, migraines, ringing in the ears, or even hair loss. Studies that include every kind of long COVID are less likely to find answers, and the best long COVID research carefully selects specific types of patients.
Q. What causes long COVID?
Dr. VanElzakker: Because long COVID is a diverse phenomenon, the causes are likely diverse. For example, if one patient had a severe case of COVID that left them hospitalized, some of their long-term symptoms may have a lot to do with tissue injury that occurred when they were sick. But for patients who had a mild or moderate case of COVID and still feel sick, there are several theories. One straightforward possibility is that the virus was never fully cleared and persists in a reservoir that drives inflammation and symptoms, at least in a subset of patients. Evidence of active SARS-CoV-2 or viral proteins like the spike protein have been found in blood samples and tissue biopsies of some people with long COVID.
Q. How long does long COVID last?
Dr. VanElzakker: We don't know the answer because COVID is so new, but some people who got sick in the first wave more than four years ago are still ill. Most people with COVID symptoms report feeling fully recovered within three months (and often within a few days or weeks). There are also many cases in which recovery takes longer than three months, but people report eventually returning to normal.
Q. Are certain people more at risk for long COVID?
Dr. VanElzakker: Given that most people have now had COVID, but only a subset have long COVID, there must be some vulnerability. Initial severity of the illness is one factor, along with some conditions like diabetes, existing infections like Epstein-Barr virus, or existing heart or lung disease. However, not everyone with long COVID has obvious risk factors. There's a cumulative effect as well. It's probably not good news that many of us are getting repeat infections.
Q. How is long COVID treated?
Dr. VanElzakker: Most long COVID clinical care is currently focused on managing symptoms, since current clinical testing does not identify the underlying biological mechanisms driving symptoms. There are several avenues of research in ongoing clinical trials, including those using immunotherapies that support rather than suppress the immune system and different antiviral approaches. Researchers are also studying how to recognize which people are most likely to experience long COVID when they are initially infected and early treatments that might help.
Q. Does long COVID cause long term complications?
Dr. VanElzakker: Because COVID is only five years old, we are only starting to learn about the longer-term consequences of both an initial case of COVID and long COVID. Unfortunately, we know from initial studies that the risk of worsening symptoms in people with chronic diseases increases with COVID exposure. This includes heart disease, stroke, diabetes, and Alzheimer's disease in older adults. With time, we may learn of more risks.
Q. How can you protect yourself from long COVID?
Dr. VanElzakker: Vaccination reduces the risk of long COVID after an infection. In addition, people should continue to wear well-fitting KN95 masks in crowded public spaces, such as airports and stores.
Image: © Dzmitry Dzemidovich/Getty Images
About the Author
Matthew Solan, Executive Editor, Harvard Men's Health Watch
About the Reviewer
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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