How do you know if you have long COVID?

A few days after Michele Hart tested negative following a COVID infection in June 2022, she started participating in virtual meetings for her job. But after each call, she crawled back into bed to rest. When she returned home from a three-day work trip, more than a week after her negative test, she spent the entire weekend in bed recovering. An avid runner and hiker, she had stopped doing both because she was tired and, she thought, possibly depressed. She wondered if she would ever feel well again.

“One of the things I found myself doing after that initial 10 days was, at least once a day, Googling something like, ‘When will I be better?’” says Hart, 45, a product specialist for a school curriculum company. The answers were frustrating: “Hang in there. Some people have it like this. Some people have it like that.”

COVID symptoms often don’t end when people test negative, which usually happens after about 10 days. Symptoms can last for weeks, months, or more. In one of the latest studies on lingering symptoms, researchers in Scotland surveyed more than 31,000 people who’d had symptomatic infections and found that 42 percent reported they had not fully recovered between six and 18 months after their infection began.

But when do ongoing COVID symptoms officially become long COVID, and how can someone know if they have a chronic condition or symptoms that will go away eventually?

Those are tricky questions without satisfying answers, says Michael VanElzakker, a neuroscientist at Harvard Medical School and Massachusetts General Hospital. Long COVID, while an active area of research, is not a clearly defined condition with specific medical criteria. There is no single diagnostic test to confirm it and no easy way to explain what is causing symptoms. Many studies are ongoing, but answers are still a work in progress.

“A core question still remains,” VanElzakker says. “Why do some people seem to fully recover, and some don’t?”

What is long COVID?

There is still no medical consensus about what the condition should be called, which symptoms it encompasses, how long a person must be sick before being diagnosed with it, or exactly how many people experience it.

Symptoms need to persist for at least three months after a probable or confirmed COVID infection to meet the World Health Organization’s definition of a post-COVID condition. The U.S. Centers for Disease Control and Prevention considers four weeks long enough to suspect long COVID, which is also called post-acute sequelae of SARS CoV-2 infection (PASC), long-haul COVID, chronic COVID, and other names.

After multiple large studies it still isn’t clear how many people are suffering from long-term symptoms, which are wide ranging. A study conducted in Germany identified 96 potential symptoms and found many of them in people who’d had prior infections. For young people, the most common symptoms included fatigue, cough, throat and chest pain, headache, fever, abdominal pain, anxiety, and depression. For adults, frequent ongoing symptoms included changes to smell and taste, fever, trouble breathing, coughing, throat and chest pain, hair loss, fatigue, exhaustion, and headache.

The Scottish study considered 26 persistent symptoms, including headaches, loss of taste and smell, tiredness, heart palpitations, constipation, breathlessness, joint pain, dizziness, and depression. But complicating the issue of diagnosis was that people who hadn’t tested positive for COVID also experienced many of those same symptoms.

While 42 percent of people in the Scottish study had some lingering symptoms, an additional 6 percent said they hadn’t recovered at all. German researchers found that adults, kids, and adolescents with a prior COVID infection were about 30 percent more likely than people without a positive COVID test to report a new condition more than three months after their infection. About 14 percent of more than 41,000 of people who responded to a CDC survey in October reported having persistent symptoms at least three months after a COVID infection.

Across studies, it looks like somewhere between one in five and one in 20 people end up with long COVID symptoms, says David Putrino, a neuroscientist at Mount Sinai Health System in New York. To him, the exact number is less important than the reality of the implications. “If any of those are true, it's an enormous number,” he says. “My clinic already has a six-month waitlist crammed out the door. None of us are sleeping. We’re all just treating 24/7.”

Will I get better?

Also unclear is the prognosis for people with lingering symptoms. Most patients who visit Mount Sinai’s Center for Post-COVID Care show some improvement within the first three months of rehab even if they experience setbacks or don’t feel fully recovered, Putrino says. But about 10 percent don’t improve.

Some might ultimately meet the criteria for myalgic encephalomyelitis or chronic fatigue syndrome, known shorthand as ME/CFS, a chronic condition that can be caused by viral infections. About 10 percent of people with severe cases of Epstein-Barr go on to develop ME/CFS, VanElzakker says. He suspects this will happen to a subset of long COVID patients.

On the flip side are people with lingering issues that ultimately go away, says VanElzakker, who lost patches of hair from his beard for several months after his own bouts with the virus. “Simply because someone doesn't feel better after three weeks,” he says, “doesn't mean they're never going to get better.”

What is causing it?

For people with ongoing symptoms, there are many potential causes, experts say, and understanding them can help guide treatment. One active area of research suggests that SARS-CoV-2, the virus that causes COVID-19, might stick around in some people’s bodies, driving inflammation and symptoms long after rapid COVID tests come up negative. In a study of 44 people who died from or with COVID in 2020 and 2021, researchers found evidence of the SARS-CoV-2 spike protein in organs including the brain, heart, and intestines that had persisted for as long as seven months, even in people who were asymptomatic. The virus replicated within tissues for up to three months in some people, the study found.

Viral reservoirs are hard to detect in living patients because they don’t show up in blood tests, VanElzakker says. He has co-founded a nonprofit called Polybio to investigate infection-associated chronic conditions like long COVID. The organization is funding research to collect gut samples from long COVID patients, and another that will collect lung tissue. He suspects that identifying where the virus ends up settling could explain the wide range of long COVID symptoms. If reservoirs get established in the gut, they could cause ongoing diarrhea, for example. In the lungs, they could cause coughing and shortness of breath.

As researchers compile evidence for viral reservoirs and other possible causes of long-term symptoms, the work is starting to guide treatment that recognizes the importance of individualized care, Putrino says. A patient with lingering symptoms from severe pneumonia and intubation, for instance, might benefit from pulmonary rehabilitation that pushes them to exert themselves. But the same kind of rehab can be disastrous for someone with post-exertional malaise who meets the criteria for ME/CFS. Antivirals might end up helping people with persistent reservoirs of COVID, but it doesn’t make sense to give these drugs to everyone with long COVID.

“Our job now is to understand who's who in this big broad diagnostic catchall,” Putrino says, “so that we can start to engage in precision medicine.”

What should I do if I still feel sick? 

If symptoms persist beyond four weeks, it’s probably time to talk with your doctor about checking your heart and lungs and running other basic tests, Putrino says. If you get to 12 weeks, he recommends a more aggressive approach with a physician or high-quality clinic that is familiar with long COVID.

Because the pandemic has been such a difficult time in so many ways, a careful check of both physical and mental health can start to distinguish between the mix of problems people might be experiencing right now, says Lucinda Bateman, medical director of the Bateman Horn Center, a nonprofit focused on research into ME/CFS, fibromyalgia, and related conditions.

Some health issues that started after a COVID infection may be related to the severe stress of living through a pandemic or to missed medical appointments due to lockdowns, clinic closures, and overbooked doctors.

For people who have been to general practitioners and specialists and still don’t have an answer, clinicians knowledgeable about ME/CFS could be helpful. They might look for signs of mast cell activation, a type of hyper-inflammation, Bateman says. Or they might consider dysautonomia, which is dysfunction of the autonomic nervous system that can be detected by looking for a drop in blood pressure or spike in heart rate when standing up. These conditions are tricky to diagnose because they can affect multiple systems and produce symptoms throughout the body, but distinctions can make a difference in medical guidance.

People don’t usually get diagnosed with ME/CFS until they have been sick for between two and five years presumably, Bateman says, because doctors have not been taught about the illness. One hope is that, with an emerging cohort of long COVID patients, clinicians might be able to catch cases earlier and prevent them from progressing—by, for example, limiting physical and even cognitive activity during recovery for some people. “We’re a culture of high-achieving and of pushing through pain, and that's the wrong advice for some conditions,” she says, “particularly for post-viral conditions that relapse with activity.”

As for Hart, her turning point came on the Fourth of July, after about a month of being sick, when she went to a concert and found that she was able to dance. There were ups and down for a couple of weeks after that, but now, six months later, she is back to full speed. “I couldn't do anything for like six weeks,” she says. “But then I was fine.”