Most people who suffer from Covid-19 fully recover. Millions of others find complete healing to be frustratingly elusive, in what’s often referred to as “long Covid.” Some experience extreme fatigue, shortness of breath and body aches, while others struggle with “brain fog” or haven’t regained their sense of smell or taste. A subset become gravely ill much later, likely because of complications from their infection. The picture that’s emerged from experience is that no single explanation, diagnosis or treatment can be applied to the growing group of people affected. Colloquially known as long-haulers, they reflect the pandemic’s lasting burden on societies and economies.
1. What is long Covid?
There’s no universally accepted definition yet. According to the World Health Organization, people with what it calls “post Covid-19 condition” have symptoms usually three months after an initial bout of Covid that last for at least two months and can’t be explained by an alternative diagnosis. Ailments may persist from the start of the illness or appear after the acute phase of the disease -- even in a person who displayed no symptoms initially. They may also fluctuate. Other groups have proposed alternative definitions. The U.K.’s National Health Service, for example, suggests referring to symptoms that last more than four weeks as “ongoing symptomatic Covid” and “post-Covid syndrome” if they persist for longer than 12 weeks and can’t be otherwise explained. Another definition may be needed for children.
2. How often does it occur?
It’s too soon to say for sure. U.S. lawmakers said in March that Centers for Disease Control and Prevention experts told them they won’t have reliable data to release for two years. The lack of a standardized way of identifying cases and other factors such as demographics and when the data were collected can lead to widely different findings. For example, research from the University of Michigan published in the Journal of Infectious Diseases in April estimated the global prevalence of post Covid-19 condition to be 43%, based on information from 50 studies spanning almost 1.7 million people worldwide. But another large study published in November, using data from the U.S. Department of Veterans Affairs, estimated that about 7% of people had at least one symptom of long Covid six months after their infection. It also found differences in symptoms by age, race, sex and baseline health status. Individuals who had severe or many symptoms initially are more likely to be affected. For instance, the study based on the VA database found the burden of long Covid beyond the first 12 weeks of illness was 4.1% among those never hospitalized for Covid, 16% among those who were hospitalized and 23% among patients who were admitted to intensive care. Other studies have found the likelihood of long Covid is greater among women, the middle-aged and the obese.
3. What are the post-Covid symptoms?
The prolonged symptoms -- sometimes entirely new to the patient -- include pulmonary, cardiovascular, gastrointestinal and nervous-system problems as well as neurological effects, such as cognitive impairment. The most commonly reported include:
4. Do variants carry different long Covid risks?
It’s possible, though there’s not been enough data collected and analyzed yet to know for sure, especially since reinfections and infections in vaccinated individuals may carry different risks of long Covid.
5. How can you prevent long Covid?
Avoiding getting infected by SARS-CoV-2, the coronavirus that causes Covid-19, is the only sure way, and vaccination is the most effective tool to reduce the risk of catching it and, more importantly, mitigate the likelihood of becoming severely ill. A U.K. study found receiving a second dose of a coronavirus vaccine at least two weeks before an infection was associated with a 41% decrease in the odds of self-reported long Covid at least 12 weeks later. Data from Israel support the finding.
6. What causes it?
Some health problems are well understood, others aren’t. For instance, survivors can experience problems as a result of:
• the direct effect of the virus on organs and tissues
• the propensity of Covid to cause bleeding and clots that can restrict or block blood vessels including in the lung, which can cause a pulmonary embolism
• excessive inflammation by the immune system
• the body’s failure to properly repair injured lungs and other organs, leading to the formation of scar tissue
• a lack of oxygen in the blood that injures the brain, lungs and other organs
• life-saving treatment, including the use of mechanical ventilation, corticosteroids, sedatives and painkillers administered in intensive care.
In a study published in January, scientists at the Fred Hutchinson Cancer Research Center and the University of Washington in Seattle found the risk of long Covid is increased by multiple early factors, including antibodies directed against their own tissues or organs known as autoantibodies, and a resurgence of the Epstein-Barr virus. Based on what’s been observed with other viral diseases and research so far, other scientists speculate that different biological and genetic factors may be driving symptoms, none of which are mutually exclusive. These may include:
• chronic, systemic inflammation
• immune dysregulation, such as when the body’s immune system overreacts or underreacts to a foreign invader
• interactions with the host microbiome, or microorganisms living in the body
• problems with the autonomic nervous system
• the persistence of viral particles or remnants in the body.
7. How serious is it?
Most long Covid symptoms don’t seem to be life-threatening, but things like shortness of breath or fatigue can be disabling. In addition, for some Covid survivors, the infection may represent a pernicious insult on the body that damages vital organs and exacerbates other diseases, the effects of which may not become apparent for months, like a ticking time bomb. Some of the conditions that may manifest later include cardiac arrest, stroke, heart failure, pulmonary embolism, myocarditis and chronic kidney disease. Doctors have also noted an uptick in cases of diabetes linked to Covid. A study in February based on the VA health-care database in the U.S. found the virus may significantly increase a person’s risk of heart disease for at least a year after recovery -- even if the person wasn’t hospitalized. Other studies from the U.S., U.K. and Germany showed that people who were hospitalized for Covid have an increased risk of being readmitted or dying 6 to 12 months later.
8. Do people recover from long Covid?
The health trajectories of Covid survivors vary widely -- from a complete resolution and a return to previous level of health in most people, to needing lung transplants in a small minority. In a subset of people, especially those whose initial infection was relatively severe, symptoms appear to be stubbornly persistent. A large study from Wuhan, the Chinese city where the pandemic virus was first detected, published last year found almost one in two Covid patients experienced persistent symptoms a year after leaving the hospital. A U.K. study of hospitalized patients published in January found that a year after discharge, fewer than 3 in 10 patients reported feeling fully recovered. It’s possible the use of treatments for Covid, including monoclonal antibody therapies and antiviral medications, reduces the likelihood of long Covid, though this hasn’t been demonstrated. There is emerging evidence that multidisciplinary rehabilitation services can improve a patient’s prospects of recovery.
9. Is Covid-19 definitely to blame for these symptoms?
Not necessarily. Some symptoms might occur by chance or be triggered by stress and anxiety, while some pre-existing conditions, such as diabetes, might have gone undiagnosed until Covid prompted medical attention. Social restrictions, lockdowns, school and business closures, loss of livelihood, decreases in economic activity and shifting priorities of governments all have the potential to substantially affect mental health, according to a study that appeared Oct. 8 in the Lancet. It found the pandemic has resulted in an extra 53.2 million cases of major depressive disorder and an extra 76.2 million cases of anxiety disorders globally. Diagnostic uncertainties 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.
10. What are the broader implications?
Some researchers say the pandemic represents an emerging global crisis, potentially spurring a raft of long-term problems such as chronic fatigue syndrome, dementia, Parkinson’s disease, diabetes and kidney impairment. The disability attributable to long Covid could account for as much as 30% of the pandemic’s health burden, researchers at the London School of Hygiene & Tropical Medicine estimated. An uptick in treatments for depression, anxiety and pain has stoked concern of a spike in suicides and opioid overdoses. The U.S. CDC reported a surge in overdose deaths in the 12-month period ending April 2021. Several surveys of long Covid sufferers indicate the condition is leading to reduced work schedules and absenteeism that has implications for the workforce and labor productivity. With more than 500 million confirmed infections worldwide as of April 2022, even a small share with long-term disability could have enormous social and economic consequences. The U.S. Government Accountability Office said in a March 2 report that long Covid could affect the broader U.S. economy through decreased labor participation and an increased need for use of Social Security disability insurance or other publicly subsidized insurance.
11. Do other pathogens cause prolonged illness?
Yes. While the development of long-term symptoms is sometimes framed as novel or mysterious, scientists say it’s actually an expected phenomenon. Most well-studied viral or bacterial pathogens have been linked to the development of chronic symptoms in a subset of infected patients. For example, post-viral syndromes can occur after the common cold, influenza, HIV, infectious mononucleosis, measles, Ebola and hepatitis B. Diabetes and other long-term consequences were observed in survivors of severe acute respiratory syndrome, or SARS, which is caused by a related coronavirus. 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 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. Long Covid shares characteristics with many other long-term health conditions, including chronic fatigue syndrome and a blood-circulation disorder known as POTS. Studies into the drivers of long Covid could improve understanding of the causes of these conditions also.
12. What is being done?
In the U.S., the National Institutes of Health was allocated $1.15 billion in funding to support research into the long-term effects of Covid. The studies hopes to get at issues such as the underlying biological causes and how they might be treated and prevented. Some researchers are pressing governments to focus attention on potential long-term organ damage. For example, researchers have shown the virus 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 vaccination, prompting researchers 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.
(Adds study on global prevalence in section 2)
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