November 29, 2021
At this stage of the coronavirus pandemic, it is clear that post-COVID syndrome is not as rare as previously hoped.
Penn State University researchers estimate that more than half of the people diagnosed with COVID-19 experience so-called "long COVID" up to six months after recovering.
Other estimates don't go quite that high, but they are still substantial.
In a study published in JAMA Network Open, about 30% of participants experienced persistent symptoms more than six months after their COVID-19 diagnoses. And the American Academy of Physical Medicine and Rehabilitation estimates that long COVID affects 3-14 million U.S. residents.
Though there is a greater recognition of this condition, the scientific community is still searching to understand why only certain people get it and the best ways to treat it.
Recent studies suggest that long COVID's similarities to chronic fatigue syndrome may hold some clues.
People with long COVID experience various symptoms that last weeks or months after their initial illnesses. They include shortness of breath, pain in the chest or joints, fatigue, brain fog and post-exertional malaise – symptoms that worsen with physical or mental exertion, according to the U.S. Centers for Disease Control and Prevention.
Headache, heart palpitation, sleep problems, mood changes, fever and dizziness also are common. Some people develop an autoimmune condition that can affect multiple organs including the heart, lung, kidney and brain.
The main symptom of chronic fatigue syndrome is extreme fatigue that lasts for at least six months, but it also is associated with a constellation of symptoms including poor sleep quality, dizziness and memory and concentration difficulties.
Doctors have not been able to identify an underlying medical condition that triggers chronic fatigue syndrome, but some experts believe a past viral infection, such as Epstein Barr and glandular fever, could be to blame for some patients. Trauma and environmental chemical exposures also are possible triggers.
People with chronic fatigue syndrome also may experience chronic sore throats, headaches, unexplained muscle or joint pain and enlarged lymph nodes in the neck or armpits.
There are no specific treatments for either condition, leading to depression and anxiety for many patients. Some experts suspect that the similarities of the two conditions could lead to new treatment approaches for both conditions.
Studies have suggested that long COVID and chronic fatigue syndrome not only share symptoms, but similar biological markers.
One study published by the Mayo Clinic found nearly half of long COVID patients have the same symptoms as people with chronic fatigue syndrome and therefor meet the criteria for a CFS diagnosis.
Brain fog, fatigue, pain and post-exertional malaise appear to be core symptoms of both long COVID and chronic fatigue syndrome, they found.
An article published in the Proceedings of the National Academy of Sciences also found the conditions share similar biological markers, including oxidative stress, systemic inflammation, a low metabolic rate and an impaired ability to generate adenosine triphosphate – an important source of energy.
"The body's response to infection and injury is complex and covers all body systems," said Bindu Paul, a pharmacology and molecular sciences professor at Johns Hopkins University. "When that response is in disarray – even just one aspect of it – it can cause feelings of being tired, brain fog, pain and other symptoms."
These findings have led to a call for more research on long COVID to involve a comparison to chronic fatigue syndrome on a molecular level.
Some of that research is already underway in New Zealand.
Warren Tate, a biochemistry professor at the University of Otago, has contributed to research suggesting chronic fatigue syndrome primarily is the result of an immune system dysfunction. He helped identify molecular changes that occur with the symptoms of chronic fatigue syndrome. Now, he is using that knowledge to better understand long COVID and other post-viral illnesses.
In both illnesses, immune system dysfunction most likely sets off a hyper-inflammatory state throughout the body and molecular changes in the DNA, Tate told Radio New Zealand.
Advocates for long COVID and chronic fatigue syndrome patients hope that focusing on the shared pathways of the two illnesses will lead to better treatment options, according to NBC News. Right now, there are no Food and Drug Administration-approved treatments for either condition.