What we (don’t) know about Covid-19’s long-term health effects

Some people with Covid-19 are sick long after the infection leaves.
Some people with Covid-19 are sick long after the infection leaves.
Image: Reuters/Mario Anzuoni
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Lucy Bailey, 32, noticed something was off during the last week of April.

She and her partner, who live in London, had stomach problems over the weekend. He got better, but after her nausea eased, she started coughing in fits while on the phone with her boss. One day, she found herself with chest pains, gasping for air. Paramedics told her she likely had Covid-19, even though she couldn’t get a test as a non-essential worker. They had seen a lot of unconfirmed cases like hers.

Her doctor confirmed the likely diagnosis, but wasn’t too worried. She was healthy. She had mild exercise-induced asthma, but that had never stopped her from running frequent 5ks. “The doctor said, ‘Given your age and health status, I see no reason why you shouldn’t recover,’” says Bailey.

And yet: “It was two months [this past] Saturday, and I’m finally just able to go back to work,” she says. She’s now working from home, but her extreme fatigue keeps her from signing on more than three half days per week.

Bailey’s experience with Covid-19 isn’t unique. The World Health Organization estimates that most mild cases of Covid-19 should resolve in two weeks. But a growing number of people, even those with mild cases, report feeling symptoms after six, eight, and even 12 weeks.

Online support groups on Facebook and independent sites have thousands of members, each of whom is navigating lingering symptoms their doctors can’t explain. Some are still easily winded, losing their breath after taking a flight of stairs. Some develop blood clots, which can lead to strokes or kidney problems. And others complain of extreme fatigue—the kind that chains you to your couch for days at a time—and neurological weariness that makes planning and focusing difficult.

So far, scientists have collected little data on these individuals. They’re not battling a Covid-19 infection, but they’re not fully recovered either. For patients that fall in the cracks, medical professionals are scrambling to offer supportive care. Here’s how they’re beginning to explain the long-term health effects of Covid-19 infections.

SARS but sneakier

To tackle the mystery of slow recoveries, scientists start with what they know about SARS-CoV-2, the virus that causes Covid-19.

Unfortunately, even that reservoir of knowledge is shallow; SARS-CoV-2 hasn’t even been around for a year. But scientists can borrow a bit from the virus’ cousin, SARS-CoV, a coronavirus from just over a decade ago that infected 8,000 people.

Both SARS-CoV and SARS-CoV-2 infect cells through ACE2 receptors; both coronaviruses cause respiratory symptoms because cells in the lungs have a high number of ACE2 receptors compared to other cells in the body.

SARS-CoV needs to be around a lot of ACE2 receptors, which is why its ideal home is the lungs. But “SARS-CoV-2 doesn’t need that many ACE2 receptors,” says Panagis Galiatsatos, a pulmonologist at Johns Hopkins Bayview Medical Center. The virus that causes Covid-19 can worm its way into any cell with an ACE2 receptor, regardless of the concentration. That includes cells along the back of the throat, in the digestive tract, in the heart, in the kidneys, and even in the brain.

The virus’s ability to infect so many types of cells is partially responsible for symptoms not typically associated with respiratory infections. Covid-19 symptoms can include gastrointestinal distress like diarrhea and vomiting, or neurological problems, like losing a sense of taste and smell or dizziness.

It also means that people with Covid-19 can have more severe complications, depending on which other organs have been infected. Now, scientists realize that SARS-CoV-2 can result in damage to the kidneys and heart either directly, or through additionally clotting in the blood that passes through these organs. These additional infection sites, Galiatsatos says, “rocked our world.”

From recovering to rebuilding

Knowing that Covid-19 can impact all of these organs, it’s not all that surprising that some people feel its effects long after their health care providers would have predicted.

For those with so-called “mild” cases that did not require hospitalization yet continue to linger, there are two likely explanations, Galiatsatos says. It could be that Covid-19 is exacerbating existing conditions that the body was able to compensate for previously.

Galiatsatos gives the example of having mild asthma that seems to have disappeared: “Your lungs are smart,” he says. “They strengthen some parts and other parts stay diseased.” Maybe, after a Covid-19 infection, the healthy parts of the lungs aren’t able to compensate anymore—and the original asthma comes raring back.

The second factor to consider is the healing process itself. After beating back an infection, it’s the immune system’s job to repair organs that have been damaged. (Sometimes the immune system is cleaning up its own mess if it launches too much of an inflammatory response.) Usually, the immune system is pretty good at making these repairs. But sometimes, it’ll MacGyver imperfect solutions: Scars, for example, form in places in the lungs that the virus has damaged; this tissue may never be able to perform the gas exchange that it used to.

Both newly-reawakened conditions and failed healing from Covid-19 could have consequences for a person’s long-term health. But scientists still aren’t sure about the range of these effects. There hasn’t been enough time to complete such studies. Researchers at King’s College London and Massachusetts General Hospital and the University of California San Francisco are collecting some of these data now.

As the pandemic wears on, it’s clear that those who have been infected may not be out of the woods once their doctors have said they’ve recovered. By documenting these long-term effects, scientists will hopefully nail down a root cause—and with that, treatments to support complete recovery.