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Scientists are learning more about the lingering symptoms of COVID-19


One of the surprising aspects of COVID-19 is that, in some people, symptoms can linger for months. This phenomenon is called long COVID, and it's had a profound impact on lots of people. In the coming weeks, NPR will be digging into some of the big, unsettled questions surrounding long COVID, and NPR's Michaeleen Doucleff is here to answer perhaps the biggest question of all - what exactly is long COVID? Michaeleen, take it away. What is it?

MICHAELEEN DOUCLEFF, BYLINE: Well, right now the picture is starting to become a bit clearer. There's actually been a lot of confusion about what long COVID is, even among scientists. And the problem is with this term - long COVID. Doctors, researchers, the media, everyone has been using this one term now for over a year, but really, what everyone is talking about is likely three different things that have all been lumped together into this one term, and each of these three things has its own set of characteristics and risks.

MARTÍNEZ: All right, so what are these different types of long COVID?

DOUCLEFF: Yeah. So let's start with the - kind of the clearest, most well-defined one. It also has the highest risk. And this is what happens when a person has, like, a really severe form of COVID.

MARTÍNEZ: OK, so you're talking about people who end up in the hospital.

DOUCLEFF: Yeah, in the hospital, in the ICU, on ventilators. In these cases, people have very severe infections. They can have life-threatening pneumonia. And scientists say this bad infection and even the body's response to fight it off can damage organs and tissues. So people can have scarring in their lungs, inflammation in their hearts, even their brains and nerves. And being that sick, regardless of the cause, is going to take time to recover. I talked to Dr. Zackary Berger about this. He's a bioethicist and internist at Johns Hopkins University.

ZACKARY BERGER: There's a very well-known symptom of people that have critical illness, and it takes a long time to recover after critical illness. So I think it's not surprising that people with COVID that lands you in the ICU would take longer to recover.

DOUCLEFF: So several studies have shown that for these people, the risk of long COVID is about 50%.

MARTÍNEZ: Fifty percent. All right, so severe disease puts you at high risk. But what about people who got mild or moderate illnesses?

DOUCLEFF: Yeah, so one thing is very clear. There is a large group of people who have had moderate, even mild, cases of COVID who report lingering symptoms three to nine months afterwards. These include things like fatigue, muscle pain, headache, difficulty breathing, even anxiety or depression. But the key question here is, are these symptoms something unique to SARS-CoV-2 infections, or are they something that actually arise with many infectious diseases but no one had been paying attention to them?

MARTÍNEZ: So you mean things like maybe the flu or pneumonia can cause lingering symptoms as well?

DOUCLEFF: Yeah, that's exactly the question I posed to Dr. Berger. He says that many people, even medical professionals, tend to think that when you're sick with an infection, it always goes away after a few weeks.

BERGER: There's this model that you get your disease, you get your treatment, you're done, you go back to work, you know, you're fine. At first, for a lot of people, it's just not like that. Plenty of people have lingering symptoms after infectious diseases. I think it's just - it's something to realize.

DOUCLEFF: For instance, take a bout of pneumonia, which SARS-CoV-2 can cause.

BERGER: If somebody has pneumonia - right? - you think you treat the pneumonia with the antibiotics; they're done. Well, they're not done. Half of people have problems breathing a month after pneumonia - half of people. That's a lot of people.

DOUCLEFF: The same goes for the flu. There was a study recently that demonstrated this beautifully. It found that after the flu, 40% of people had at least one lingering symptom that looks similar to long COVID. So what might be happening with the second group is there are people who just take longer to recover from an infection, whether it's the flu, pneumonia or COVID-19.

MARTÍNEZ: So for lack of a different word - long flu, long pneumonia.

DOUCLEFF: Yeah, it's like a post-viral syndrome.

MARTÍNEZ: Now, what about that third group?

DOUCLEFF: Yeah. So after you take into account these first two types, so people who are really seriously ill and people who are just taking time to recover from a viral infection, what's left is something that's likely specific to SARS-CoV-2, and it may be tied to the virus invading an organ or tissue or, perhaps, persisting there or some lingering inflammation caused by the body fighting off the infection. And what's emerging is that this syndrome seems to be a collection of symptoms, including shortness of breath, brain fog, fatigue, but also an issue with one particular organ or tissue - for example, in your heart or your nerves - which causes other symptoms, like a fast heart rate or loss of smell.

MARTÍNEZ: Well, then how common, then, is this type of long COVID that's specific to this coronavirus?

DOUCLEFF: You know, it's not exactly known yet. But Dr. Claire Steves has been working hard to nail down an estimate. She's a geriatrician at King's College London and has been analyzing data from the Office of National Statistics in the U.K.

CLAIRE STEVES: Generally speaking, the rates of long COVID is around the sort of - just under 5% of people who get COVID infection, that kind of level. And that's, I suspect, probably one of the most accurate figures.

DOUCLEFF: So that's 5% for symptoms more than three months after an infection. So if we're trying to arrive at the best definition of a disorder specific to COVID, this 5% seems to be the best ballpark figure we have right now.

MARTÍNEZ: Well, five is a low number. I mean, it doesn't seem too bad, 5%.

DOUCLEFF: That's - you know, it doesn't seem that bad, right? But, you know, given how many people have had COVID in the U.S., that's at least 2 million people with lingering symptoms. Now, here's the good news. Steves says that the percentage drops off drastically a year after the infection.

STEVES: There definitely are individuals that have still had symptoms for over a year, even up to now 18 months. But those individuals - there's a very small number of those individuals. And actually, we see this - and I see this clinically as well - that gradually people are getting better.

DOUCLEFF: So for most people, these symptoms do resolve.

MARTÍNEZ: What about the vaccines? Do they reduce people's risk of long COVID?

DOUCLEFF: This is the other great news. Preliminary data suggests the vaccines cut the risk of long COVID at least in half when you do get an infection. But remember; the vaccines greatly reduce your chance of getting infected in the first place. So overall, the vaccines effectively reduce the risk of long COVID by about 80% or 90%. So that really shows you the power of the vaccines. And if you want to cut your risk of long COVID, probably the best thing to do is to go get vaccinated.

MARTÍNEZ: That's NPR's global health correspondent Michaeleen Doucleff. Michaeleen, thanks a lot.

DOUCLEFF: Thank you, A.

(SOUNDBITE OF HELIOS' "VAINGLORY") Transcript provided by NPR, Copyright NPR.

A Martínez
A Martínez is one of the hosts of Morning Edition and Up First. He came to NPR in 2021 and is based out of NPR West.
Michaeleen Doucleff, PhD, is a correspondent for NPR's Science Desk. For nearly a decade, she has been reporting for the radio and the web for NPR's global health outlet, Goats and Soda. Doucleff focuses on disease outbreaks, cross-cultural parenting, and women and children's health.