Since March, we have published a series of in-depth interviews with John Swartzberg, MD, about different aspects of the coronavirus pandemic. In our most recent sit-down (via a safely distanced phone call), we asked about the emerging reports of people continuing to experience poor health after an acute episode of Covid-19, a phenomenon that’s being referred to as “post-Covid syndrome.” What lingering symptoms are patients commonly experiencing? Is this normal after a viral illness? What causes it? Here is an edited version of our conversation from late July.
What are post-viral syndromes?
We’ve known for years that after a bad case of influenza (flu), people often don’t feel well for six or eight weeks. They’re tired and fatigued and can have a lingering cough. And that’s not related to the presence of the virus. With influenza, significant amounts of the virus are present in respiratory fluids up to 24 hours before symptoms appear, and the levels start to fall a few days later. In adults, the virus is usually gone within five or six days. At six weeks, you won’t find any viral particles at all, but people can still be experiencing this post-viral condition.
The post-influenza syndrome is not unusual. When I’ve talked to patients about it, I’ve always just put it under the framework of, “You’ve been pretty sick and it takes a while to heal.” That’s a common-sense sort of explanation, not a mechanistic explanation of why it happens. But it’s an explanation that people tend to accept because it’s an experience most of us are familiar with from previous bouts of the flu.
This kind of persistent fatigue occurs after other illnesses too, but influenza has been the classic one where it’s described. With mononucleosis, for example, it’s not uncommon to see a fatigued state last for several months. But everything falls into a bell-shaped curve. You might find a rare number of cases of people who experience symptoms for many months and even up to a year after otherwise recovering from the illness. But that would be very, very unusual.
What are we seeing with the coronavirus?
I’ve seen numbers suggesting that up to 60 percent of people who have recovered from the acute phase of Covid-19 still have persistent fatigue, even three or four months later. In this case, it may be that the post-viral syndrome is affecting a much higher proportion of people and lasting a lot longer than we’re used to seeing with influenza and other illnesses.
The coronavirus that causes Covid-19 is also a very different virus than influenza, so its long-term consequences are likely going to reflect that. Before Covid-19, we had no model of a viral respiratory disease so frequently causing an overwhelming inflammatory response that can lead to extensive scarring of the lung. And this virus can also attack many other organs. While influenza typically infects solely the respiratory organs, the coronavirus has the ability to infect cells in, for example, the gastrointestinal tract, the cardiovascular system, skin, kidneys, and nervous system. And it triggers not only an inflammatory cascade but also an out-of-control cascade of blood clotting in some people.
It looks like some of the long-term impacts of this virus might be irreversible. For example, the shortness of breath is often due to lung scarring, and we think that could be permanent. The virus leads to more blood clots, and that could lead to a stroke that permanently damages the brain or, if the clot goes to the lungs, a pulmonary embolism that destroys lung tissue. In these cases, we can see the structural damage in the body and understand why the disabilities from the illness might be chronic.
What might explain the chronic fatigue after Covid-19?
It’s not clearly understood at this point. As with other post-viral syndromes, the prolonged fatigue isn’t explicable by any apparent structural damage. It could be related to a dysfunction in the central nervous system, because there seem to be a lot of nervous system effects associated with this disease. We’re seeing people with cognitive problems, for example; they’re just not as sharp as before the illness. They feel like they have “brain fog”—problems with memory and concentration. This is different from what we’re used to seeing after viral illnesses. You don’t generally see these sorts of cognitive problems persist after people have had influenza, for instance.
We also know that loss of smell has become a characteristic presentation for Covid-19, and in some people that symptom is persisting after the acute phase of the illness. It’s not clear why. There is some evidence that the virus directly attacks the olfactory nerves (nerves involved in smell), although that hasn’t been shown consistently. There are some hints that the virus could be using the olfactory nerves as a conduit to the brain.
There are no experts in coronavirus yet. It’s only been around about eight months, and physicians are keeping an open mind about what happens when it interacts with humans. It’s really been fascinating. I thought it would be an illness that would just attack our respiratory organs like influenza, and it became quickly apparent that that was the wrong model for this illness.
Some of the lingering symptoms sound similar to what’s experienced by people with chronic fatigue syndrome, also called myalgic encephalomyelitis or ME/CFS. Could the emerging post-Covid syndrome be seen as a version of ME/CFS?
That’s a really good question. We know that ME/CFS is often triggered by an infectious disease. People are then plagued with ongoing exhaustion, cognitive problems, and other symptoms, and they get much worse after even a small amount of exertion, which is called post-exertional malaise. I think the big question that everybody has is if Covid-19 is going to be a trigger for ME/CFS. Or will it be a trigger for a syndrome that ends up looking very different? For example, are post-Covid patients getting worse after exerting themselves? Or does exertion not worsen their symptoms, but something else does?
I certainly hope that seeing all of the people worldwide suffering from post-Covid syndrome will help change the longstanding attitudes toward people with ME/CFS. They have experienced a lot of prejudice over the years, with people claiming they have a psychological or psychiatric problem rather than a medical condition. People remaining sick for months on end after Covid-19 could ultimately translate into more compassion and understanding, and even better treatment, for people with ME/CFS or other poorly understood syndromes with similar clusters of symptoms. But it will take time to know. We are essentially in the middle of a global experiment right now.