As researchers continue to uncover the long list of Covid-19 symptoms, some physicians are beginning to explore the disease's possible long-term effects on patients with more severe symptoms, Lois Parshley reports for Vox. Here's what the research shows so far.

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The limited evidence on long-term effects of Covid-19

The new coronavirus and the disease it causes are still just months old, meaning researchers have not been able to study the disease's long-term effects on people.

In fact, Parshley reports, researchers are still working to understand the disease's short-term effects and treatment. Currently, it's estimated as few as 5% and as many as 80% of Covid-19-positive patients are asymptomatic or have mild cases of the illness that take days or weeks for symptoms to emerge—and many have no symptoms after two weeks, Parshley reports. A smaller percentage of patients have severe cases of Covid-19, which the World Health Organization estimates can take three to six weeks to fully recover from.

But Joseph Brennan, a cardiologist at the Yale School of Medicine, and other experts now worry there may be a subset of patients who suffer long-term damage. For instance, Parshley reports, preliminary research on other coronaviruses, such as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), suggest some people can take years to recover.

Parshley rounds up the most notable potential long-term health effects that doctors are observing in Covid-19 patients.   

Blood clotting, stroke, and embolisms

Physicians report that patients hospitalized for Covid-19 are experiencing high rates of blood clots that can cause strokes, heart attacks, lung blockages, and other complications, Parshley reports.

For instance, physicians are seeing an uptick in strokes among young patients with Covid-19.

The blood clots also can travel to other organs, leading to ongoing health problems. For instance, pulmonary embolisms, which occur when the clots block circulation to the lungs, can cause ongoing "functional limitations," like fatigue, shortness of breath, heart palpitations, and discomfort when performing physical activity, Parshley reports. Similarly, blood clots in the kidneys can cause renal failure, which can cause life-long complications.

Heart damage

Physicians have also reported an increase in inflammation of and damage to the heart muscle in Covid-19 patients. One study published in March found that out of 416 hospitalized Covid-19 patients, 19% showed signs of heart damage.

Another study from Wuhan published in January found 12% of Covid-19 patients showed signs of cardiovascular damage. Other studies have since found evidence of myocarditis, inflammation of the heart muscle that can cause scarring, and heart failure in Covid-19 patients.

Now, physicians warn that Covid-19 survivors may experience long-lasting cardiac damage and cardiovascular problems, which could increase their risk for heart attack and stroke. Doctors also warn Covid-19 could worsen existing heart problems.

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Lung damage

Research shows some patients experience lung symptoms such as pain and a dry cough, weeks after recovering from the virus.

Physicians have also found evidence of scarring in Covid-19 patients' lungs. According to Parshley, some CT scans show Covid-19 patients have light gray patches on their lungs called "ground-glass opacities," which don't always heal. One Chinese study found the patches in 77% of patients, Parshley reports.

Brennan explained that the "virus creates an incredibly aggressive immune response" that causes "spaces [in the lungs to be] filled with debris and pus, making your lungs less pliable." According to Brennan, this type of lung damage can be permanent and could result in reduced lung capacity. "Routine things, like running up a flight of stairs, would leave these individuals gasping for air," he said.

While it's too soon to tell whether the lung damage in Covid-19 patients will be permanent, research shows that about one third of survivors of similar coronaviruses such as SARS and MERS had long-term lung damage.

Ali Gholamrezanezhad, a radiologist at the Keck School of Medicine at the University of Southern California who is currently studying which patients are at higher risk of permanent lung damage, speculates underlying diseases like asthma and hypertension may put patients at greater risk of these long-term effects.

Neurological symptoms

Research shows Covid-19 can also affect the central nervous system after patients showed neurological symptoms like headaches, dizziness, loss of taste and smell, and impaired consciousness. According to researchers, symptoms were most common in patients with severe cases of the disease.

But research surrounding SARS and MERS found neurologic complications of these diseases, including muscular weakness, numbness, and burning or prickling did not occur until about two to three weeks into the course of the diseases. Other more serious complications, such as confusion and comas, were also seen in MERS patients.

As a result, Mitchell Elkind, president-elect of the American Heart Association and professor of neurology and epidemiology at Columbia University, said doctors should be "on the lookout for long-term neurocognitive problems," including decreased concentration and memory as well as dysfunction of the peripheral nerves that lead to the "arms, legs, fingers, and toes."

What this means for patients

Physicians and public health experts say more research—and time—is needed to understand the long-term effects of Covid-19 and the complications patients might encounter down the line and whether they have a chance of recovery.

"It is a true roller coaster of symptoms and severities, with each new day offering many unknowns," said Lauren Nichols, a Covid-19 survivor who experienced symptoms for eight weeks. "I may feel healthier one day but may feel utterly debilitated and in pain the next" (Parshley, Vox, 5/8).