Immunologic symptoms
Given the close link between a nonspecific viral illness and the onset of symptoms in chronic fatigue syndrome, scientists like Dr. Hornig opted to focus on immunologic symptoms. In a 2015 analysis published in Science, Dr. Hornig and colleagues showed that immune problems can be found in the earliest stages of chronic fatigue syndrome, and that they change as the illness progresses. Patients who had been sick for less than 3 years showed significant increases in levels of both pro- and anti-inflammatory cytokines, and the factor most strongly correlated to this inability to regulate cytokine levels was the duration of symptoms, not their severity. A series of other studies also revealed problems with regulation of the immune system, although no one could show what might have set these problems in motion.
Other researchers found signs of mitochondrial dysfunction in those with chronic fatigue syndrome. Because mitochondria make energy for cells, it wasn’t an intellectual stretch to believe that glitches in this process could contribute to fatigue. As early as 1991, scientists had discovered signs of mitochondrial degeneration in muscle biopsies from people with chronic fatigue syndrome. Subsequent studies showed that those affected by chronic fatigue were missing segments of mitochondrial DNA and had significantly reduced levels of mitochondrial activity. Although exercise normally improves mitochondrial functioning, the opposite appears to happen in chronic fatigue.
To Dr. Nath, these dual hypotheses aren’t necessarily mutually exclusive. Some studies have hinted that infection with the common human herpesvirus–6 (HHV-6) can lead to an autoimmune condition in which the body makes antibodies against the mitochondria. Mitochondria also play a key role in the ability of the innate immune system to produce interferon and other proinflammatory cytokines. It might also be that the link between immune and mitochondrial problems is more convoluted than originally thought, or that the two systems are affected independent of one another, Dr. Nath said.
Finding answers, especially those that could lead to potential treatments, wouldn’t be easy, however. In 2016, the NIH launched an in-depth study of a small number of individuals with chronic fatigue, hoping to find clues about what the condition was and how it might be treated.
For scientists like Dr. Nath, the NIH study provided a way to get at the underlying biology of chronic fatigue syndrome. Then the pandemic struck, giving him yet another opportunity to study postviral syndromes.
Chronic post-SARS syndrome
In March 2020, retired physician Harvey Moldofsky, MD, began receiving inquiries about a 2011 study he and his colleague, John Patcai, MD, had published in BMC Neurology about something they dubbed “chronic post-SARS syndrome.” The small case-control study, which involved mainly health care workers in Toronto, received little attention when it was first published, but with COVID-19, it was suddenly relevant.
Early clusters of similar cases in Miami made local physicians desperate for Dr. Moldofsky’s expertise. Luckily, he was nearby; he had fled the frigid Canadian winter for the warmth of Sarasota, Fla.
“I had people from various countries around the world writing to me and asking what they should do. And of course I don’t have any answers,” he said. But the study contained one of the world’s only references to the syndrome.
In 2003, a woman arrived in Toronto from Hong Kong. She didn’t know it at the time, but her preairport stay at the Hotel Metropole had infected her with the first SARS (severe acute respiratory syndrome) coronavirus. Her subsequent hospitalization in Toronto sparked a city-wide outbreak of SARS in which 273 people became ill and 44 died. Many of those affected were health care workers, including nurses and respiratory therapists. Although most eventually returned to work, a subset couldn’t. They complained of energy-sapping fatigue, poor sleep, brain fog, and assorted body aches and pains that persisted for more than 18 months. The aches and pains brought them to the attention of Dr. Moldofsky, then director of the Centre for the Study of Pain at the University of Toronto.
His primary interest at the time was fibromyalgia, which caused symptoms similar to those reported by the original SARS long-haulers. Intrigued, Dr. Moldofsky agreed to take a look. Their chest x-rays were clear and the nurses showed no signs of lingering viral infection. Dr. Moldofsky could see that the nurses were ill and suffering, but no lab tests or anything else could identify what was causing their symptoms.
In 2011, Dr. Moldofsky and Dr. Patcai found a strong overlap between chronic SARS, fibromyalgia, and chronic fatigue syndrome when they compared 22 patients with long-term SARS issues with 21 who had fibromyalgia. “Their problems are exactly the same. They have strange symptoms and nobody can figure out what they’re about. And these symptoms are aches and pains, and they have trouble thinking and concentrating,” Dr. Moldofsky said. Reports of COVID-19 long-haulers didn’t surprise Dr. Moldofsky, and he immediately recognized that Nath’s intention to follow these patients could provide insights into both fibromyalgia and chronic fatigue syndrome.
That’s exactly what Dr. Nath is proposing with the two NIH studies. One will focus solely on the neurologic impacts of COVID-19, including stroke, loss of taste and smell, and brain fog. The other will bring patients who have had COVID-19 symptoms for at least 6 months to the NIH Clinical Center for an inpatient stay during which they will undergo detailed physiologic tests.
Scientists around the world are launching their own post–COVID-19 studies. Dr. Moreau’s group in Montreal has laid the groundwork for such an endeavor, and the CoroNerve group in the United Kingdom is monitoring neurologic complications from the coronavirus. Many of them have the same goals as the NIH studies: Leverage the large number of COVID-19 long-haulers to better understand the earliest stages of postviral syndrome.
“At this juncture, after all the reports that we’ve seen so far, I think it’s very unlikely that there will be no relationship whatsoever between COVID-19 and chronic fatigue syndrome,” Dr. Hornig said. “I think there certainly will be some, but again, what’s the scope, what’s the size? And then, of course, even more importantly, if it is happening, what is the mechanism and how is it happening?”
For people like Ms. Gage-Witvliet, the answers can’t come soon enough. For the first time in more than a decade, the full-time professor of epidemiology didn’t prepare to teach this year because she simply can’t. It’s too taxing for her brain to deal with impromptu student questions. Ms. Gage-Witvliet hopes that, by sharing her own experiences with post COVID-19, she can help others.
“In my work, I use data to give a voice to people who don’t have a voice,” she said. “Now, I am one of those people.”
A version of this article first appeared on Medscape.com.