The world was slow to recognize long COVID as one of the most serious consequences of the coronavirus. Six months into the pathogen’s tear across the globe, SARS-CoV-2 was still considered an acute airway infection that would spark a weeks-long illness at most; anyone who experienced symptoms for longer could be expected to be dismissed by droves of doctors. Now long COVID is written into CDC and WHO documents; it makes a cameo in the newest version of President Joe Biden’s National COVID-19 Preparedness Plan.
But for all we know now about long COVID, it is still not enough. Researchers still don’t know who’s most at risk, or how long the condition might last; whether certain variants might cause it more frequently, or the extent to which vaccines might sweep it away. We do not have a way to fully prevent it. We do not have a way to cure it. We don’t even have a way to really quantify it: There still isn’t consensus on how common long COVID actually is. Its danger feels both amorphous and unavoidable. People already struggle to deal with well-known risks, let alone fuzzy, slippery ones. “You can be too afraid of what you don’t understand or just say, ‘It’s not well defined; I’m not going to think about it,’” says Erin Sanders, a nurse practitioner and clinical scientist at MIT. Concern, when we let it, can act like a gas. It expands to fill the space we give it.
This is a precarious position to be in with long COVID, as enthusiasm for pandemic precautions is crumbling. The Biden administration recently reinforced its stance on which COVID-19 outcomes matter most: Since we can’t stave off all infections, we’re shifting our focus to hospitalizations and deaths, a well-defined pair of metrics that we know we can prevent. Where does long COVID—a condition that can spin out of infections of all severities—fit in? “It doesn’t,” says Hannah Davis, of the Patient-Led Research Collaborative, who has long COVID.
But even if long COVID’s prevalence turns out to be a single-digit percentage of SARS-CoV-2 infections—proportionally much smaller than most experts estimate—in absolute terms “that is not small,” says Ziyad Al-Aly, the director of the Clinical Epidemiology Center at the Veterans Affairs St. Louis Health Care System. Millions of people have already developed long COVID; many of them, an untold fraction, have not recovered. This is the challenge of chronic illness: When people join its ranks, they do not always exit. With each new case of long COVID, the virus’s burden balloons.
“I worry, now that everyone is moving to the post-pandemic world, we’re going to sweep all these patients under the rug,” Al-Aly told me. Long COVID struggled to gain a toehold in the national consciousness; now it threatens to be one of the first major COVID impacts to slip back into the margins.
Researchers have known for many months that long COVID is more a category than a monolith. Al-Aly very roughly likens it to the way we talk about cancer—an umbrella term for diseases that are related but that require distinct diagnoses and treatments. Long COVID has hundreds of possible symptoms. It can batter the brain, the heart, the lungs, the gut, all of the above, or none of the above. The condition can start from a silent infection, an ICU-caliber case, or anything in between. It can begin days, weeks, or months after the virus first infects someone, and its severity can fluctuate over time. “We lump all of that into one broad thing,” Al-Aly said. “It is not.”
The condition’s root causes, accordingly, are also diverse. In some cases, long COVID may be collateral damage from the war waged between virus and immune system; in others, it might sprout out of a chronic SARS-CoV-2 infection or, conversely, a quick viral encounter that sets bodily systems on the fritz. These hypotheses aren’t comprehensive or mutually exclusive: There are only so many ways for bodies to run smoothly, and infinite ways to throw those processes out of whack.
All of this means that even diagnosing long COVID—an essential step toward understanding it—is still a battle. We don’t have a clear-cut, consensus clinical definition, a single name for the condition, or a standardized set of tests to catch it. Even the CDC and the WHO can’t agree on how long a person must be sick before they meet the condition’s criteria. Some researchers and health-care providers favor one agency’s definition; others, dissatisfied with both, come up with their own. And “there are still doctors out there that do not think long COVID exists,” says Alexandra Yonts, a pediatric-infectious-disease specialist at Children’s National Hospital, in Washington, D.C. That makes researching the condition fraught, and studies less uniform. Davis, of the Patient-Led Research Collaborative, says many efforts are peppered with problems that misrepresent long COVID’s burden. Some studies miss cases because they omit many of the condition’s most common symptoms, for instance, or because they exclude the many long-haulers whose illness comes and goes. Others can botch the numbers when they neglect to include information about long-haulers’ baseline health before infection, or when they fail to establish good control groups of uninfected and infected people who don’t go on to develop long COVID’s chronic symptoms. Too many studies, Davis told me, have “inadvertently included COVID-infected people in their negative control groups” because they rely on fallible tests that can’t adequately determine who’s actually caught the virus.
In an ideal experimental world, to understand long COVID’s risks, researchers would systematically survey large swaths of the population over long periods of time, watching to see who gets infected, who goes on to develop the condition, what form it takes, and how it impacts people’s health, says Shruti Mehta, an infectious-disease epidemiologist at Johns Hopkins University who is studying long COVID. But few institutions have the resources for such an undertaking, which could span many months or years. So many researchers have to make do with the limited data sets that are already available to them. As a result, some studies end up biased toward patients who were hospitalized, while others wind up favoring people who have the time, means, and trust in the health-care system to sign up for long-term studies. Neither group fully captures long COVID’s wide-ranging toll. The situation’s especially tough for pediatric patients, who might be too young to articulate the severity of their symptoms and are often excluded from long-COVID studies. Long COVID certainly exists in kids, but it may not perfectly mirror what goes on in adults: Children’s susceptibility to the virus is different, and their bodies are so rapidly changing, says Yonts, who runs a pediatric-long-COVID clinic in D.C.
All told, the study of long COVID has become, as Sanders of MIT puts it, “a data disaster.” Some researchers estimate that a single-digit percentage of SARS-CoV-2 infections bloom into long COVID; Al-Aly is one of them. Others, meanwhile, favor larger numbers, with a few even insisting that the rates are actually more than half. Most of the experts I spoke with said they feel comfortable working in the 10 to 30 percent range, which is where many studies seem to be starting to converge. Finding one answer is tricky, without knowing how many forms long COVID can take—some could be more common than others. Formally splitting the disease into subdivisions could help address some of these ambiguities. But we don’t know nearly enough to start slicing and dicing, says Bryan Lau, an infectious-disease epidemiologist working with Mehta and Priya Duggal.
If researchers aren’t comprehensively capturing who currently has long COVID, they can’t say for certain who’s most likely to get it either. Many researchers have found that women contract long COVID more frequently than men. Others have uncovered evidence that people who end up infected with gobs of the coronavirus, or who produce antibodies that attack the body’s own tissues, also seem to tilt toward long COVID. Chronic health issues, including diabetes, could up a person’s chances of getting sick and staying sick as well. So might a lingering Epstein-Barr virus infection. But some of these trends are still being confirmed, experts told me, and the extent to which they toggle risk up or down isn’t known. And it’s definitely too early to pinpoint any of these factors as long-COVID causes. “For acute COVID, we know what the risk factors are,” Akiko Iwasaki, an immunologist studying long COVID at Yale, told me. “For long COVID, it’s much less clear.”
Still, a couple of other variables feel a bit more nailed down. “The risk is high in people who need hospitalization or ICU care,” Al-Aly said. Deepti Gurdasani, an epidemiologist at Queen Mary University of London, says she’s fairly confident that the nature of a person’s exposure to SARS-CoV-2 plays a role as well: Heavier and more frequent viral encounters seem to tip the scales toward symptoms that last and last. That’s a concern for people in essential occupations, who “aren’t able to shield themselves,” she told me.
If these last few factors directly affect how and whether long COVID unspools, vaccination—which reliably staves off hospitalization and, to a lesser degree, infection—could be a partial preventive. Several studies have shown that shots do seem to muzzle long-COVID rates. (Other interventions that lower exposure also help: masks, distancing, ventilation.) They don’t, however, eliminate long COVID’s odds. To date, experts have yet to find any demographic that has been spared from the condition, despite persistent myths that certain groups, particularly kids, are somehow immune. “We’ve seen it in children of all ages,” says Laura Malone, a pediatric neurologist at the Kennedy Krieger Institute, in Baltimore. Some of her patients are toddlers. The virus isn’t pulling any punches either. Every iteration we’ve encountered so far, Omicron included, seems capable of causing long COVID. “No one is not at risk,” Al-Aly said.
To this day, most countries do not keep a running tally of long-COVID cases. But ballparks of the burden are staggering. Some 2 percent of all U.K. residents—not just those with documented infections—might currently have long COVID, according to the Office for National Statistics. Another analysis estimates that up to 23 million Americans have developed the condition since the pandemic’s start. More will join them. But Davis worries that those numbers will continue to be left off of national dashboards, and thus out of the public eye. Now that the federal government has tightened the boundaries of its concern to hospitalizations and deaths, the public does not even really have to look away from the national perspective on long COVID: There is next to nothing to see.
As people rack up different combinations of shots and infections with different variants, what worsens or soothes long COVID is also getting harder to understand. Many of the experts I’ve spoken with over the past two years have told me that while they think long COVID is essential to study, it’s too complex for them to want to tackle themselves. Meanwhile, long COVID remains the pandemic’s looming specter. We are told there is risk, but not exactly how much; we are told that avoiding long COVID would be ideal, but lack the practical guidance to do so—the virus is so widespread that eventual infection, for many people, feels almost inevitable.
At the same time, as researchers look deeper and deeper into the bodies of infected people, they’re only seeing more damage. With each passing month, more studies emerge documenting how the coronavirus alters the function of vital organs such as the heart and the brain. The public has been cultured to think that most SARS-CoV-2 infections are trivial, and the repercussions brief, especially for the young, healthy, and privileged. But long COVID breaks the binary of severe and mild. “It’s going to continue to affect people, even people who are protected from severe illness during the acute phase of infection,” Michael Peluso, an infectious-disease physician and long-COVID researcher at UC San Francisco, told me.
No matter where the true numbers on long-COVID risk sit, they are too large to ignore. “Whether it’s 10 percent or 50 percent, at both levels you have to do something about it,” Gurdasani said. Statistics will help sharpen and clarify the condition’s boundaries, and are still worth seeking out. They will not, however, change long COVID’s threat, at its core.
Davis, who is nearing her second anniversary of developing long COVID, feels this deeply. She is still experiencing cognitive dysfunction and memory loss. Her heart still races when she stands. “You cannot live your life like you used to,” she told me. “Your life just becomes this shell.” For individuals, for societies, “this is not going away.” Even after much of the world puts the pandemic in its rearview, long COVID will keep filling hospitals and clinics. It will dot the pages of scientific texts, and linger in the bodies of millions of people worldwide. Hospitalizations and ICU admissions are not the only COVID outcomes that can buckle a health-care system.
That strain is already being felt by the health-care workers on long COVID’s front lines. Yonts, the Children’s National pediatrician, told me that she’s currently booking patients “out to Memorial Day.” COVID’s global crisis can, in some ways, end when we decide to treat it as done. But that is not an option for a growing fraction of the planet, who cannot put COVID fully behind them. “This is going to be the pandemic after the pandemic,” Gurdasani said.