What Is Long Covid? Doctors Explain Why It Causes Extreme Symptoms in Long-Haulers

Some COVID-19 patients are still having symptoms weeks after their initial infection passed. “They had issues like fatigue, brain fog, chest pain, shortness of breath, racing heart, GI symptoms, and anxiety and depression,” says Dr Joan Bosco. “It was surprising, because some of the least sick patients initially wound up being the sickest down the road.”

Today we call them “long-haulers”—people who struggle with a range of puzzling, often debilitating, symptoms after a bout with the novel coronavirus—and many have been suffering for months. While some studies say only patients who have had symptoms for 12 weeks or more qualify as having post-COVID syndrome (PCS), many doctors say anyone who has persistent symptoms for four weeks after a COVID infection should talk to a doctor. 

What is post-COVID syndrome?

Estimates of how many people develop post-COVID syndrome vary from 2% to 25% or more. Interestingly, PCS seems to affect more middle-aged adults than older adults, but as of yet no one knows for certain why it happens or whom it’s most likely to affect.

“That doesn’t mean it’s not real,” says Dr Laurie Jacobs. “Many of my post-COVID patients say their doctors dismissed and disregarded their symptoms, which compounds their suffering.”

Shayna Zweiback, 27, who fell ill with COVID-19, was one of those patients. Prior to the pandemic, Zweiback had suffered from depression, which was then exacerbated by her physical health issues.

"Everyone told me my depression was the cause of my post-COVID symptoms. They made me feel like my illness was my fault,” she says. After Zweiback recovered, she felt better for a couple of months. Then out of nowhere her health began to rapidly deteriorate. “First I developed extreme fatigue and brain fog,” she says. “I’d forget what I was talking about in the middle of a conversation, I had trouble distinguishing between letters and numbers, and it took me a day to recover my energy from a walk down the block or a trip to the grocery store.” She also struggled with shortness of breath. “It felt like air hunger,” Zweiback recalls. Now she knows her physical symptoms are what’s worsening her mental health, not the other way around.

What causes post-COVID syndrome?

It’s important to note that SARS-CoV-2 (the novel coronavirus) isn’t the first virus to cause lasting symptoms, says Dr Greg Vanichkachorn, medical director of Mayo Clinic’s COVID Activity Rehabilitation Program. “Previous viral outbreaks, like SARS and MERS, left some people debilitated for months—sometimes years,” he says. “The virus isn’t still alive and active in people with ongoing symptoms, but it triggers a response in the body that causes persistent symptoms. Now we’re trying to figure out what that response is. At this point, we have some likely suspects.”

Excess inflammation

The leading candidate is immune-system related inflammation. “We see high levels of inflammation in many of our post-COVID patients,” says Dr Christian Sandrock, a specialist in emerging infectious diseases. In fact, when researchers in Europe did MRIs of the hearts of 100 patients who had recently recovered from COVID-19, they found that 60% had ongoing heart inflammation—which can cause some of the symptoms many long-haulers report, like shortness of breath, chest pain, and elevated heart rate with exertion. What’s more, that inflammation affected people regardless of their preexisting conditions or how sick they were when they initially had the virus.

An autoimmune response

In some long-haulers, COVID-19 might have triggered an autoimmune response, in which the immune system mistakenly targets the body’s healthy tissue instead of the virus, says Dr Vanichkachorn. Researchers at Yale University recently found that COVID-19 patients had large numbers of auto-antibodies, immune molecules that attack healthy tissue, compared to people without the virus. And autoimmune diseases, like lupus and rheumatoid arthritis, commonly cause fatigue and digestive issues, two common post-COVID symptoms. It may be that the same mechanisms behind those conditions are causing the same symptoms in people with PCS.

Problems with the nervous system

Many PCS patients show symptoms of dysautonomia, which refers to a dysregulation of the autonomic nervous system (responsible for involuntary functions, like blood pressure, heart rate, breathing, and digestion).

“Dysautonomia affects blood flow, including blood flow to the brain, so it can cause fatigue, headaches, brain fog, and exercise intolerance,” says Dr Vanichkachorn. “When we test patients with post-COVID syndrome, they often have some autonomic dysfunction, so it’s probably a piece of the puzzle, at least for some people.”

Blood clots and blood vessel damage

Tiny blood clots could be playing a role, too. Many patients have high levels of a protein in the blood which indicates that their blood is extra prone to clotting. “And when we put them on medication to prevent clotting, they feel better,” says Dr Sandrock.

The likely reason COVID-19 patients frequently develop blood clots: The virus can infect and damage the cells lining the blood vessels, says Dr William Li, one of the authors of a recent study conducted by an international group of researchers. This lining is ordinarily smooth and slippery, like an ice rink, says Dr Li, which allows blood to flow easily throughout the body. But when the endothelial cells lining the vessels become damaged, they get sticky, which causes platelets in the blood to adhere to the vessel wall, forming clots.

“We’ve now examined tissue from people who died of COVID-19 and found widespread clots everywhere there were infected blood vessels—the lungs, brain, heart, kidneys and other organs,” he says. “These tiny blood clots interrupt normal blood flow and damage organs. When they occur in the lungs they can cause shortness of breath. Microclots in the heart may contribute to palpitations.” Endothelial damage has been found in the brains of people with COVID-19 and may contribute to brain fog and cardiac damage.

How to protect yourself

Post-COVID syndrome is challenging, says Dr Vanichkachorn, because most patients have multiple symptoms. Dozens of studies of long-haulers, which will one day provide answers, are underway worldwide. “We’re essentially building the plane while we’re flying it,” says Dr Vanichkachorn.

In the absence of clear scientific answers, doctors who treat PCS sufferers say the best way to protect yourself from post-COVID syndrome is to not get infected with the virus in the first place. “This isn’t the ‘just the flu’,” says Dr Bosco. “People need to understand there can be long-term consequences from a COVID-19 infection and take all the precautions necessary, including wearing masks, washing their hands, and social distancing to prevent infection.”

If you do get COVID-19, make sure you take plenty of time to recover before jumping back into regular activities. “We know from both SARS and chronic fatigue syndrome patients that if you push too hard you experience a setback,” Dr Vanichkachorn says. “We have post-COVID-19 patients who were marathon runners. Now they count it as a victory to walk across the bedroom without feeling breathless. Recovery is slower than most people would like. But we’re seeing gradual improvement in most of our patients.”

Zweiback acknowledges the slow progress can be incredibly frustrating. She makes time to rest, tries to avoid stress, eat regular healthy meals, and stays hydrated. “I’ve been sick for 13 months, and I’m probably 65% recovered. If I’ve learned one thing, it’s that I have to pay attention to my body, rest when I start feeling tired, and be patient.”