Millions of people who have gotten Covid-19 and survived are finding that a full recovery can be frustratingly elusive. Weeks and months after seemingly recovering from even a mild case, many patients confront a wide range of health problems. As researchers try to measure the durability and depth of what’s being called “long Covid,” a burgeoning number of specialized post–acute Covid clinics are opening to handle the patients. The scale of the pandemic means that Covid’s disabling effects -- as well as economic pain and drain on health resources -- could persist well after the contagion ends.

1. What are the ailments?

Data are emerging on the scope, frequency and duration of ailments -- ranging from mildly annoying to incapacitating -- that emerge or linger four weeks or more after a SARS-CoV-2 infection. Fatigue, shortness of breath, chest pain, cognitive disturbances including “brain fog,” and joint aches are commonly reported problems, often bad enough to affect quality of life. Specific organ dysfunction also has been reported involving primarily the heart, lungs, and brain, even among those who had no noticeable symptoms during the acute phase. Although most long Covid symptoms don’t seem to be life-threatening, sufferers had a 59% increased risk of dying within six months, a study published April 22 in the journal Nature found. That works out to about eight extra deaths per 1,000 Covid patients -- adding to the pandemic’s hidden toll amid growing recognition that many people require readmission to the hospital, and some die, weeks after their viral infection has abated.

2. How prevalent is it?

We don’t know yet because Covid-19 is a new disease. Risks may vary between hospitalized and non-hospitalized patients and be influenced by the severity of illness, age, gender, race, income, and underlying medical conditions. Researchers haven’t studied enough patients over a long enough period of time to gauge the full range of long-term effects -- what doctors call the post-acute sequelae, or PASC -- what proportion of patients will suffer from them, or for how long. Early findings and the demand for specialized clinics to help survivors deal with scarred lungs, chronic heart damage, post-viral fatigue and other debilitating conditions indicate a significant prevalence.

3. What are the estimates?

The U.K.’s Office of National Statistics estimated in December that, among people who have tested positive for Covid-19, about 1 in 5 exhibit symptoms for five weeks or longer, and about 1 in 10 have symptoms for 12 weeks or longer. As of November, before England experienced a severe winter surge, some 186,000 Covid survivors were living with symptoms that had persisted for 5 to 12 weeks, out of over 1 million known cases. A small study from the University of Washington reported persistent symptoms for as long as nine months after an acute bout of Covid-19. A much larger study involving almost 240,000 Covid-19 patients found one in three received a neurological or psychiatric diagnosis within six months of infection.

4. Is Covid-19 definitely to blame for these symptoms?

Not necessarily. One difficulty is figuring out which conditions are directly related to a past infection with SARS-CoV-2 and what might occur by chance or be triggered by pandemic-induced stress and anxiety. A study of health-care workers at a Swedish hospital compared persistent symptoms among those who had recovered from mild Covid-19 at least 8 months before, and those who never caught the coronavirus. Among those who’d been infected, 8% reported lingering symptoms causing moderate-to-marked disruptions of their work life, compared with 4% in the non-infected group. Uncertainties about post-Covid illness have sometimes led to what so-called long haulers describe as medical gaslighting by health professionals who don’t take their complaints seriously, especially if the patient is a woman.

5. What are the broader implications?

Some researchers say the pandemic may spur a raft of long-term problems, such chronic fatigue syndrome, also called myalgic encephalomyelitis or ME, dementia, Parkinson’s disease, diabetes and kidney impairment. An uptick in treatments for depression, anxiety and pain has stoked concern of a future spike in suicides and opioid overdoses. The reduced work hours reported in 68.9% of long-Covid patients indicate the pandemic is crimping labor productivity. With 136 million Covid cases worldwide, even a small share with long-term debility could have enormous social and economic consequences. And these will be be magnified if people end up enduring years or decades of coronavirus-related disability.

6. Do other viruses cause prolonged illness?

Yes. Post-viral syndromes occur after many viral infections, including the common cold, influenza, HIV, infectious mononucleosis, measles and hepatitis B. Diabetes and other long-term consequences were observed in survivors of severe acute respiratory syndrome (SARS), which is caused by a related coronavirus. A Canadian study found 21 health-care workers from Toronto had post-viral symptoms for as long as three years after catching SARS in 2003, and were unable to return to their usual work. Some people who were hospitalized with SARS in Hong Kong still had impaired lung function two years later, a study of 55 patients published in 2010 found. Still, it’s not known yet whether the lessons of SARS are applicable to Covid-19.

7. What’s being done?

In the U.S., Congress is providing $1.15 billion in funding over four years for the National Institutes of Health to support research into the long-term effects of Covid-19. The series of studies hopes to answer key questions, such as:

• What does the spectrum of recovery look like across all age groups, and what proportion experience long-term problems?

• What is the underlying biological cause of these prolonged symptoms, and how might they be treated and prevented?

• What makes certain people vulnerable, while others recover fully and quickly?

• Does SARS-CoV-2 infection trigger changes in the body that increase the risk of chronic disorders affecting the heart, brain or other organs?

(Updates to add mortality risk in section 1 and suicide risk in section 5.)

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