As early as summer 2020, reports began to emerge of people continuing to experience poor health, including lingering fatigue, after an acute case of Covid-19. Now called post-acute sequelae of SARS-CoV-2 infection (PASC)—or more simply post-Covid syndrome or long Covid—the phenomenon affects more than 20 percent of people who’ve had and recovered from Covid, according an analysis of the private health care records of nearly two million people diagnosed with Covid in 2020. Sadly, as we enter yet another wave of infections around the country, the absolute number of people with lingering symptoms will continue to rise.
Post-Covid syndrome is highly surprising, actually, since such effects have been seen after other viral illnesses. But what causes it? Are the lingering symptoms after Covid different from those seen after other viruses? And are they reversible?
Here are excerpts from an interview with John Swartzberg, M.D., chair of our editorial board and an expert in infectious diseases, about this syndrome.
Wellness Letter: What are post-viral syndromes?
Dr. John Swartzberg: We’ve known for years that after a bad case of influenza (flu), people often don’t feel well for six to eight weeks or so. 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 in the framework of, “You’ve been pretty sick and it takes a while to heal.” That’s a commonsense 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. With mononucleosis, for example, it’s not uncommon to see a fatigued state last for several months. But these things tend to fall on a bell-shaped curve. You might find a rare number of people who experience symptoms for many months or even up to a year after otherwise recovering from the illness.
WL: What are we seeing with the new coronavirus?
JS: I’ve seen data suggesting that up to 60 percent of people who have recovered from the acute phase of Covid-19 still have persistent fatigue, even 8 to 12 months later—though it’s going to be a long time before we know how often this really occurs in both adults and kids. In any case, it appears 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 a very different virus from those that cause influenza, so its long-term consequences are likely going to reflect that. Before Covid-19, we had no model of a viral respiratory disease that so frequently causes an overwhelming inflammatory response, leading to extensive scarring of the lung. 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, cardiovascular system, and nervous system, as well as the kidneys and skin. And it triggers not only an inflammatory cascade but also an out-of-control cascade of blood clotting in some people.
Additionally, we know that loss of smell has become a characteristic presentation of 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), though that hasn’t been shown consistently. There are hints that the virus could be using the olfactory nerves as a conduit to the brain.
WL: Do we know how long such symptoms might last? Could they become chronic?
JS: Unfortunately, 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, to a pulmonary embolism that destroys lung tissue. The virus can also damage the heart in a variety of ways, possibly resulting in long-term cardiac issues. In these cases, we can see the structural damage in the body and understand why the disabilities from the illness might be chronic.
WL: What might explain the lasting fatigue after Covid-19?
JS: 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 other viral illnesses. You don’t generally see these sorts of cognitive problems persist after people have had influenza, for instance.
WL: Some of the lingering symptoms sound similar to those experienced by people with chronic fatigue syndrome, also called myalgic encephalomyelitis or ME/CFS.
JS: There are similarities. 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 is whether 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 is it not exertion but something else that’s worsening their symptoms?
Seeing all of the people worldwide suffering from post-Covid syndrome might help change longstanding attitudes toward individuals with ME/CFS, who have experienced a lot of prejudice over the years, with their symptoms often attributed to 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 those with ME/CFS or other poorly understood syndromes that have similar clusters of symptoms. But it will take time to know. We are essentially in the middle of a global experiment right now.
WL: Any last thoughts to share?
JS: Physicians are keeping an open mind about what happens when Covid-19 interacts with humans. I thought it would be an illness like influenza that would just attack our respiratory organs, but it quickly became apparent that that was the wrong model.
