Studies estimate that 10 to 30 per cent of people report persistent or new medical issues months after their initial coronavirus infections. Photo / Mark Mitchell
Among the many confounding aspects of the coronavirus is the spectrum of possible symptoms, as well as their severity and duration.
Some people develop mild illness and recover quickly, with no lasting effects. But studies estimate that 10 per cent to 30 per cent of people report persistent or new medical issues months after their initial coronavirus infections — a constellation of symptoms known as long Covid.
People who experience mild or moderate illness, as well as those without any underlying medical conditions, can nonetheless experience some debilitating long-term symptoms, including fatigue, shortness of breath, an erratic heart rate, headaches, dizziness, depression and problems with memory and concentration.
Such lingering medical issues are so varied that one study by a patient-led research group evaluated 203 symptoms that may fluctuate or even appear out of the blue after people seem to have recovered.
As Dr Ziyad Al-Aly, the chief of research and development at the VA St Louis Healthcare System and a clinical public health researcher at Washington University in St Louis, said, "If you've seen one patient with long Covid, you've seen one patient with long Covid."
There is little consensus on the exact definition of long Covid, also known by the medical term PASC, or post-acute sequelae of Covid-19.
While the World Health Organisation says long Covid starts three months after the original bout of illness or positive test result, the Centers for Disease Control and Prevention sets the timeline at just after one month.
Some researchers and healthcare providers use other time frames, making efforts to study and quantify the condition more difficult, said Al-Aly, who has conducted many studies on long-term post-Covid issues.
When patients experiencing persistent symptoms go to their doctors, tests like electrocardiograms, chest X-rays, CT scans and blood work don't always identify physiological problems, Al-Aly said. Researchers are working to pinpoint certain biological factors, called biomarkers, that correlate with persistent Covid symptoms. These could include signs of inflammation or certain molecules produced by the immune system that might be measured by blood tests, for example.
For now, doctors must rely on their patients' descriptions of symptoms and rule out alternative explanations or causes. Some post-Covid clinics have multidisciplinary teams of specialists evaluate patients to figure out the best treatment options.
It's unclear what exactly drives long Covid, but research has begun to offer some clues. Some experts theorise that an immune response that goes into overdrive when you first get sick may lead to inflammation and damage throughout the body, eventually resulting in long Covid symptoms, said Dr Michael Peluso, an infectious disease physician at the University of California, San Francisco.
"We know that during acute Covid-19, some people have a really revved-up immune response and some people have a reduced immune response, and that response can determine the trajectory of how well somebody does," he said.
Another explanation, experts say, could be that your immune system never fully shuts down after the initial infection.
Research offers some hints about which patients might face a greater risk of long-term symptoms. In a study of 209 patients published in January, researchers found four factors that could be identified early in a person's coronavirus infection that appeared to correlate with an increased risk of having ongoing symptoms two to three months later.
One factor was the level of coronavirus RNA in the blood early in the infection, an indicator of viral load. Another was the presence of autoantibodies — antibodies that mistakenly attack tissues in the body as they do in conditions such as lupus and rheumatoid arthritis. A third factor was the reactivation of Epstein-Barr virus, which can cause mononucleosis and infects most people, often when they are young, and then usually becomes dormant.
The fourth factor was having Type 2 diabetes, although experts say that in studies involving larger numbers of patients, diabetes might be only one of several medical conditions that increase the risk of long Covid.
Studies from post-Covid clinics have also found other preexisting medical conditions that may put people at risk for long Covid. In a report on the first 100 patients treated for neurological and cognitive symptoms at a post-Covid clinic at Northwestern Memorial Hospital in Chicago, 42 per cent reported previously having depression or anxiety, although such patients might simply be more comfortable seeking neurological treatment, doctors said. Other preexisting conditions included autoimmune diseases and headaches.
Studies also suggest that the risk of developing long Covid peaks in middle age, Peluso said. The average age of patients in the Northwestern study was 43. An analysis of 78,252 private health insurance claims across the United States found that people between the ages of 36 and 64 made up about two-thirds of the long Covid patients. (But that study did not include most Medicare recipients, so it involved relatively few older patients.)
Women may be disproportionately affected, with some studies finding that about 60 per cent of patients are female. A similar pattern has emerged in other long-term conditions like ME/CFS (myalgic encephalomyelitis/chronic fatigue syndrome), which has several symptoms similar to those of long Covid.
Because the pandemic has had a significant effect on Black and Latino communities in the United States, and those groups have more limited access to medical care, they may have high numbers of long Covid cases as well, Peluso said.
The picture is still coming into focus, but several studies suggest that getting a Covid vaccine can reduce — but not eliminate — the risk of longer-term symptoms.
The United Kingdom's Health Security Agency conducted an analysis of eight studies that had looked at vaccines and long Covid before mid-January. Six found that vaccinated people who then became infected with the coronavirus were less likely than unvaccinated patients to develop symptoms of long Covid. The remaining two studies found that vaccination did not appear to conclusively reduce the chances of developing long Covid.
In that analysis, one study, which has not been peer-reviewed, of about 240,000 US patients found that those who had received even one dose of a Covid vaccine before their infections were seven to 10 times less likely than unvaccinated patients to report symptoms of long Covid 12 to 20 weeks later.
But another large study of electronic patient records at the US Veterans Health Administration, also not yet peer reviewed, found that those who were vaccinated had only a 13 per cent lower risk than unvaccinated patients of having symptoms six months later. Vaccinated patients mostly benefited by being less likely to develop lung problems and blood-clotting difficulties, said Al-Aly, one of the study's authors.
"Reliance on vaccination as a sole mitigation strategy is wholly inadequate," Al-Aly said. "It is like going to battle with a shield that only partially works."
If you are concerned about any lingering symptoms after a confirmed or suspected coronavirus infection, don't be afraid to ask for help. Checking in with your primary care provider is a good first step. More doctors are becoming aware of long Covid symptoms and can recommend tests that might at least rule out other causes of your symptoms.
Some long Covid issues can be managed with existing medications or treatments for symptoms like headaches or gastrointestinal problems. Physical therapy and "cognitive rehab", including approaches often used for patients who have experienced strokes or brain injuries, can also be helpful over time.
Some people benefit from tailored physical and mental health rehabilitation services and breathing exercises, which can help them slowly build back strength and endurance for physical activities.
Other possible tools against long Covid, including antiviral treatments, are only beginning to be studied. The National Institutes of Health is devoting more than US$1 billion (NZ$1.5b) to a major research effort called the Recover Initiative, but progress has been slow so far. Lawmakers are pushing for better funding for long Covid research and medical care.
People with long Covid may also want to consider joining a research trial, Peluso said. You may be able to find continuing clinical studies at universities and academic centres near you.
"Participating in research can be very empowering," Peluso said.
This article originally appeared in The New York Times.
Written by: Knvul Sheikh and Pam Belluck
© 2022 THE NEW YORK TIMES
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