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It doesn’t have a formal name or a definition. No one can predict who will develop it, but whether you call it long Covid or post-acute Covid-19 or just identify yourself as a long-hauler, the constellation of prolonged symptoms after Covid-19 infection has become all too familiar.

About one-third of people who were sick enough to need hospitalization — including supplemental oxygen or mechanical ventilation to breathe — still struggle with problems affecting their bodies and their minds four weeks or more after the first onset of symptoms. About 1 in 10 people who had Covid but were never admitted to a hospital report they experience bewildering brain fog, shortness of breath, muscle weakness, or crushing fatigue in the months after the first signs of their initial illness. Some see no end in sight; others seem to recover.

To help understand how to recognize and treat this mysterious condition, researchers from Harvard and Columbia culled the scientific literature to guide treatment for nine organ systems where the SARS-CoV-2 virus does its damage. Kartik Sehgal, an author of a review published Monday in Nature Medicine and a medical oncologist at Dana-Farber Cancer Institute and Brigham and Women’s Hospital, talked to STAT about what’s known and unknown. This conversation has been condensed and lightly edited.


What is the most pressing problem to address about long Covid?

The most important question right now is, how can we help identify patients who may be at higher risk of long Covid? Studies so far have suggested that patients who had severe Covid-19 have higher chances of having these persistent or lingering effects. There’s also concern for patients who have preexisting respiratory conditions such as asthma, patients who are elderly, or patients who have multiple other medical conditions. Obesity has been associated with increased incidence of long Covid. These patients are theoretically at higher risk of long Covid, but these are all observations of physicians, all in the context of the limited data which is available so far. There is a need to look at these questions in a coordinated manner, in a more systematic manner, so that it can all come together.


If it’s too early to say who might develop long Covid, is the cause still unknown too? Are there any theories?

Courtesy dana-farber cancer institute
Kartik Sehgal, a medical oncologist at Dana-Farber Cancer Institute and Brigham and Women’s Hospital Dana-Farber Cancer Institute

There are a couple of hypotheses or likely possibilities. None of them has been proven so far, but they include: Is there a viral reservoir? Is virus hiding in some of the organs? Maybe there is no virus, but some components of the virus, like proteins or RNA or genetic material of the virus, are lurking, and it’s causing a low-level activation of the immune system. So that’s one of the hypotheses. The other one is essentially the immune response during the acute infection was so severe that it caused long-term changes in the composition of the immune system. It’s like an autoimmune phenomenon: Autoantibodies, instead of fighting the virus or the bacteria, start attacking the normal body organs. So [we need] to delineate what is the role of the viral reservoir versus the immune system? It may be overlapping, and it doesn’t have to be exclusive. It would be helpful in terms of coming up with a more definitive management of this phenomenon.

There have been stories about people with long Covid feeling better after vaccination. Can you explain that?

There have been a lot of anecdotal reports about this. We do have a possible hypothesis, even though we have not proven it and we cannot make recommendations based on it. The possible explanation could be that if there are certain low levels of virus hiding in a reservoir in the body or viral genetic material, the immune system may be getting activated by the vaccine and may be able to take care of that. But again, this is not proven. This is just a hypothesis right now. And then the vaccine may also have an effect on the immune system and may help in terms of redirecting it from whatever may be causing long Covid. There is scientific feasibility behind this, but not enough data. We are recommending everyone get their Covid vaccine, and this could be another reason for patients who may have had Covid. 

How should patients be cared for?

One of the guidelines, which has come from the United Kingdom, is to consider follow-up after 12 weeks for all patients who were hospitalized. And that includes getting a chest X-ray and getting regular blood work. For patients who required ICU-level care and if they required a breathing tube and mechanical ventilation, they have recommended a shorter follow-up, at four weeks from the time of discharge, with more focus on the lungs. If someone is having some persistent symptoms at the time of hospital discharge but no longer requires being in the hospital, they need to be followed sooner. 

What about people who never went to a hospital?

It’s very important not to exclusively focus on patients who require hospitalization and not to dismiss their concerns without having a proper evaluation for all other explanations. This was essentially one of the key messages highlighted by patient advocacy groups and patient support groups, and then eventually by the media. They have played a major role in the recognition that it’s not just patients who require hospitalization.

Are there differences depending on the race or ethnicity of the patient?

There is one study from the United Kingdom that found an association of [Black, Asian, or ethnic minority patients] with the likelihood of having lingering shortness of breath. But there are multiple other factors which play into it, including biological factors, socioeconomic factors, and those extraneous factors that are systematic racism. All of those factors need to be looked into very carefully, and we should not make hasty judgment in making those associations. It has actually been identified as a research priority by the National Institutes of Health to look into those factors. I think a lot more data is required to be able to answer these questions in a more fair and systematic manner. 

What is your message to patients?

I think it’s very, very important to make sure, especially for our vulnerable populations, they know that they’re not alone in experiencing these symptoms. And if they are having persistent symptoms, then they need to reach out to their doctor. 

What is the role of patient groups?

If any good has come out of the pandemic, even though it’s not been perfect, it’s been the coordination and the collaboration between patient advocacy groups as well as physicians and the community in getting information from each other, having a two-way road, spreading the message that they are not alone in experiencing these lingering effects.

  • I have two friends on different continents, one older & retired, one middle-aged hard worker, who are still struggling with low energy, brain-fog, decreased lung function, decreased kidney function, memory challenges. They are both tough women, in no way this is “in their head”. It appears to me that it might be time for a new medical specialty : “long-xxxx” and in this case : long-covid.

  • It’s also only fair to say that a decent % of long covid sufferers may be entirely psychosomatic. As many as half of them have never tested positive for SARS-CoV2. Even antibody blood tests come back negative in around 1/3 of long covid patients.

    This either flies in the face of the two theories proposed in the article, OR it’s something worth following. Maybe this people did have covid but didn’t mount a proper immune response. Or maybe it’s all in their head, brought on by the understandably massive amounts of stress that people are under. Either way, clearly it’s widespread and we need to figure out a reason.

  • As someone who’s wrestled autoimmune rheumatoid disease for years, everything I see & hear about long-haulers, feels and sounds exactly like rapid onset acute (flares) to moderate/severe autoimmune disease. The only possible upside is that is likely to pour scrutiny onto AI and perhaps even a cure… before I die would be fabulous. But it breaks my heart to see so many people understand now how AI steals your life. I wish the rush to find solutions didn’t need to be due to the suffering of others.

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