What we know and don’t know about long COVID
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The lack of diagnostic tools for long COVID-19 make the condition difficult to conclusively identify or study.
Studies place the prevalence of long COVID-19 anywhere between 4 percent and 48 percent of people who have been infected with the virus.
Other aspects of the condition, such as how long symptoms may persist and how common it will be in the future, also remain unclear.
After two years of research and one of the largest public health campaigns in human history, doctors and scientists don’t yet have a test to detect the mysterious affliction called long COVID-19, let alone a head count of the afflicted.
Based on the latest wave of studies, long COVID-19 may beset 4 percent of the population who catch the virus, or 14.8 percent, or 48 percent. Its toll on the body spans dozens of possible symptoms, from fatigue to chest pains to fuzzy thinking to hair loss. The symptoms overlap with those seen in scores of other illnesses.
Many long COVID-19 cases clear up after several months or a year. Some seem to be permanent. Only time will tell.
“What do we mean when we say long COVID? We’re still figuring it out,” said Dr. Josh Fessel, a senior clinical adviser and COVID-19 specialist at the National Institutes of Health (NIH). Along the way, he said, “we’re learning a lot about what recovery looks like after a significant illness.”
A long COVID-19 study released last week by Scottish researchers raised eyebrows around the globe. Six to 18 months after COVID-19 infection, 48 percent of people surveyed said they had not fully recovered.
That report is an outlier. The World Health Organization puts the prevalence of long COVID-19 at 10 to 20 percent. Other recent estimates range across the map. An ongoing survey by British health officials, updated in July, found long COVID-19 in only 4 percent of cases. A Canadian government survey, updated this week, found that 14.8 percent of adults with COVID-19 retained symptoms three months after infection. A U.S. government survey, updated this month, found that 30 percent of adults who had the coronavirus believed they had experienced long COVID-19.
For many Americans, long COVID-19 now looms as a larger worry than acute COVID-19, the first round of disease triggered by the viral invader. Vaccinations and weakening variants have vastly lowered the odds that people without underlying conditions will wind up hospitalized or dead from the acute version of the ailment.
“People don’t talk about just getting COVID any more,” said Tara Leytham Powell, professor of social work at the University of Illinois. “Long COVID is more of a fear.”
Ashley Drapeau caught COVID-19 in December 2020. A month later, she said, “it just seemed like it wasn’t getting any better. I was still having shortness of breath. I was having migraines. … Lack of appetite, nausea. It seemed to go on and on.”
Drapeau took most of 2021 off. Now she’s back at work, running a long COVID-19 program at the George Washington University Center for Integrative Medicine. She’s operating at “about 80 percent.” She has never fully recovered.
In calculating the prevalence of long COVID-19, researchers struggle to gather basic data. There is no way to conclusively diagnose long COVID-19, so most research relies on self-reported information obtained through surveys. Respondents don’t always know if they had COVID-19. They can only guess.
“There’s no test. There’s no way to evaluate it,” said Dr. Priya Duggal, an epidemiologist and professor at the Johns Hopkins Bloomberg School of Public Health. “You can only ask people to report it themselves.”
Duggal works on an ongoing long COVID-19 survey at Johns Hopkins, a project that began with the first reports of lingering illness in the spring of 2020.
“We expected there would be a long-term consequence,” she said. “We weren’t expecting what we’re seeing now.”
Hopkins researchers have found that one-third of patients report symptoms of long COVID-19. A much smaller group, around 3 percent, was identified as suffering from severe long COVID-19, “meaning that they can’t function in their day-to-day life,” Duggal said. “They can no longer walk a quarter of a mile, or up a flight of stairs. Can’t do things like vacuum. It affects their ability to do their jobs, take kids to school.”
Though researchers have not reached consensus on some of the specifics, they generally agree that long COVID-19 is a constellation of symptoms that can endure for months or years after infection, sometimes emerging after an illusory recovery. The most common symptoms seem to be fatigue, shortness of breath and that blurry mental state known as COVID fog.
Researchers often file long COVID-19 sufferers into two groups. The smaller contingent, perhaps 1 to 5 percent of all coronavirus cases, suffer symptoms so severe that they “can’t live normal lives,” Duggal said. The larger camp of COVID-19 “long-haulers,” somewhere between 5 and 50 percent of all cases, manifest relatively mild symptoms that don’t hinder daily routines of work, school, shopping and sleep.
Some in that camp may not have long COVID-19 at all.
In the Scottish study, 91 percent of people who believed they had long COVID-19 reported one or more symptoms associated with the affliction. But at least one of the same symptoms appeared in more than half of the group that had never caught COVID-19.
Some people confuse essentially random symptoms with resurgent COVID-19, experts say. Others could be coping with the vagaries of recovery from a serious illness. Still others may be fighting symptoms that linger mostly in the mind.
“A lot of these are symptoms of depression and anxiety,” said Dr. Steven Dubovsky, chairman of psychiatry at the University of Buffalo. “I’m sure there’s a population of people who got sick and stayed sick for complicated psychological reasons. That doesn’t mean they aren’t sick.”
One problem with diagnosing long COVID-19 lies in the bewildering array of symptoms. One recent Dutch study counted 23. More common: loss of taste and smell, muscle pain, back pain, headache and lethargy. Less common: “heavy arms and legs,” stomach pain, diarrhea and tingling extremities.
“We talk about long COVID like it’s a thing,” said Fessel of NIH. “And I think the truth is that what we’re learning, and what we’ve had a sense of for a while, is that there are different flavors of long COVID. It seems like there are some people who really have a lot of the fatigue, the cognitive changes. … There are people who don’t have much of that, but they’re really short of breath with activity levels that never used to bother them, and that persists for months. There are people with real high heart rates. All of these fall under the umbrella of long COVID.”
One uncertainty lies in the very definition of “long.” Some researchers define long COVID-19 as symptoms enduring past three or four weeks. Others draw the line at three months.
Another imponderable: Fickle public interest in COVID-19 surveys. People who haven’t recovered from the virus may be more likely to answer a long COVID-19 survey than people who have. Educated white women, in particular, seem to answer these surveys at markedly higher rates than people in other demographic groups.
Not all the news about long COVID-19 is bad. One good tiding: Keeping up with vaccines seems to reduce the chances of contracting long COVID-19.
U.K. health officials have found encouraging signs that weaker variants, as well, correlate to lower rates of long COVID-19.
“Our research and other research have found that if you’re fully vaccinated, your risk of having long COVID 12 weeks after an omicron infection is about half what it was with delta,” said Daniel Ayoubkhani, principal statistician at the U.K. Office for National Statistics.
Other researchers disagree. And even if the rate of long COVID-19 decreases over time, owing to vaccination or milder variants, the sheer number of infections should guarantee a steady stream of long COVID cases for a long time to come. The impact of those cases, on individuals and on society, could be massive. One recent study suggests long COVID-19 may have already sidelined 4 million American workers.
“That’s over $100 billion a year, in terms of lost wages,” said Drapeau, of George Washington University. “That’s a pretty big deal.”
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