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 still confront a wide range of health problems. As researchers try to measure the duration and depth of what's being called “long Covid,” a burgeoning number of specialised post-acute Covid-19 clinics are opening to handle the patients.
The scale of the pandemic means that Covid-19's disabling effects – as well as the economic pain and drain on health resources – could persist well after the contagion ends.
1. What are the ailments?
A constellation of symptoms have been reported among people who don't return to their pre-Covid-19 level of health. Researchers are still documenting the spectrum of recovery and trying to understand the different outcomes patients may experience.
Symptoms can range in severity from annoying to incapacitating, and may be linked to specific organ dysfunction involving the heart, lungs and brain – even in individuals who had no noticeable sign of illness when they were infected with SARS-CoV-2, the coronavirus that causes Covid-19.
Fatigue, shortness of breath, chest pain, joint aches and cognitive disturbances including “brain fog” are commonly described problems that emerge or linger four weeks or more after an infection.
Although most long Covid-19 symptoms don't seem to be life-threatening, a study published in April in the journal Nature found that coronavirus survivors were 59% more likely to die within six months compared with people who escaped Covid-19. That works out to about eight extra deaths per 1,000 Covid-19 patients – adding to the pandemic's hidden toll.
2. How prevalent is it?
Although data are emerging, 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 – what proportion of patients will suffer from them, or for how long.
Early findings and the demand for specialised clinics to help survivors deal with scarred lungs, chronic heart damage, fatigue and other conditions indicate a significant prevalence.
About 1 million people in the U.K. alone – 1.6% of the population – were experiencing self-reported “long Covid” at the beginning of May, with almost two-thirds experiencing a negative impact on day-to-day activities.
People ages 35 to 69, women, those living in the most-deprived areas and those with an existing disability or health condition were most likely to report symptoms.
A large Danish study of people whose infections didn't require hospitalisation found the absolute risk of severe, post-acute complications was low, but also noted increases in general practitioner and outpatient hospital visits, which could indicate lingering symptoms.
3. How long do symptoms persist?
Data are still emerging. 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.
A separate U.K. study found 7 in 10 patients had not fully recovered five months after discharge. 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. A large study based on data from a U.S. health plan published in The BMJ in mid-May found that 14% of people infected with the coronavirus developed one or more related conditions requiring medical care beyond the acute phase – but so did 9% of the people in an unaffected control group.
Some conditions in Covid-19 survivors 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.
In some critical Covid-19 cases, life-saving treatment itself may cause post intensive care syndrome, a complication that includes anxiety, depression and post-traumatic stress disorder and muscle weakness.
Uncertainties about conditions attributable to Covid-19 have sometimes led to what patients 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 as chronic fatigue syndrome, dementia, Parkinson's disease, diabetes and kidney impairment.
An uptick in treatments for depression, anxiety and pain has stoked concern of a spike in suicides and opioid overdoses. The U.S. Centers for Disease Control and Prevention reported a surge in overdose deaths in 2020.
The reduced work hours reported in 69% of patients, colloquially known as long haulers, indicate the pandemic is having an impact on labour productivity.
With almost 150 million confirmed infections worldwide as of late April, even a small share with long-term debility could have enormous social and economic consequences. And these will be magnified if problems end up lasting for years or decades.
6. Do other viruses cause prolonged illness?
Yes. So-called 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 coronavirus related to SARS-CoV-2.
A Canadian study identified 21 health-care workers from Toronto who 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 is being done?
The U.K. government in December published guidelines for identifying, assessing and managing the long-term effects of Covid-19. 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 questions such as what are the underlying biological causes and how might they be treated and prevented. Some researchers are pressing governments to focus attention not only on infection and vaccination rates but potential long-term organ damage.
For example, researchers have shown SARS-CoV-2 can infect insulin-producing pancreatic tissue, potentially triggering diabetes that in some cases persists beyond the acute infection.
That's prompted Australia's Monash University and King's College London to create a global registry for studying “new onset” diabetes.
Some long haulers have reported feeling better after receiving a Covid-19 vaccination, prompting researchers in April to examine the phenomenon and whether vaccines can offer clues to treatment.
Avindra Nath, clinical director of the U.S. National Institute of Neurological Disorders and Stroke, said vaccines, including for flu, have been known to help patients with chronic fatigue, but relief has almost always been temporary.