New evidence suggests chronic fatigue may be a side effect suffered by survivors of the coronavirus.
Early research suggests the infection is mild in four out of five cases, with most making a full recovery.
Now, however, a small number of survivors appear to be suffering from lingering complications after the virus has been cleared from the body – what is being referred to as post-COVID syndrome.
The director of the US National Institute of Allergy and Infectious Diseases, Dr Anthony Fauci, says an “extraordinary” number of survivors have developed symptoms “strikingly similar” to chronic fatigue syndrome.
“It's extraordinary how many people have a post-viral syndrome that's very strikingly similar to myalgic encephalomyelitis/chronic fatigue syndrome,” Dr Fauci told Medscape.
An official survey of 292 people who overcame the infection found more than a third (35%) were lacking energy two to three weeks after testing positive.
It gels with reports from actor Tom Hanks, 63, who complained of feeling “very fatigued all the time” when he and wife Rita Wilson caught the infection while filming in Australia in March
The Academy Award winner and his wife made a full recovery after two weeks.
‘Strikingly similar’ to chronic fatigue syndrome
Chronic fatigue syndrome, also known as myalgic encephalomyelitis (ME), generally leaves patients feeling extremely tired and generally unwell.
In severe cases, a patient may be unable to carry out day to day activities, which may affect their mental health.
As of 2018 it is estimated that Chronic Fatigue Syndrome affects 250,000 Australians. Of that number, 25% or 62,500, are severe or very severe and believed to be housebound or bedbound
In the US, between 836,000 and 2.5 million Americans were thought to have the condition in 2015, however, most were undiagnosed.
What is Chronic Fatigue Syndrome?
Although it is unclear exactly what causes chronic fatigue, it can be triggered by viral infections like glandular fever.
Most patients improve over time, however, some never make a full recovery.
Post-viral fatigue, feeling exhausted, can also theoretically occur after fighting off any virus.
“Even after you clear the virus, there are post-viral symptoms,” Dr Fauci said.
“I know, because I follow on the phone a lot of people who call me up and talk about their course.
“It's extraordinary how many people have a post-viral syndrome that's very strikingly similar to myalgic encephalomyelitis/chronic fatigue syndrome.”
Of the 292 survivors, the US Centers for Disease Control and Prevention (CDC) surveyed, 274 developed at least one similar symptom while infectious.
When interviewed two to three weeks after testing positive, these patients each reported around seven of the centre’s 17 symptoms. Thirty-five per cent noted unresolved fatigue.
The Department of Health lists the primary symptoms of the virus as fever, coughing, sore throat, and shortness of breath.
The US’s definition is considerably broader, including less common symptoms from headaches, to runny nose and nausea or diarrhoea.
‘Feels like a living death’: Chronic fatigue’s impact on sufferers
Research has suggested it can take a while for coronavirus survivors to get fully back on their feet.
According to the UK government, the infection’s tell-tale cough or loss of smell or taste can “last for several weeks once the infection has gone”.
It also seems mild cases seem to resolve in a couple of weeks, while more severe cases can stretch up to six weeks, according to analysis of early data out of Chinese done by the World Health Organization.
Research has suggested people who do develop Chronic Fatigue do so when the activation fo the immune system in response to the virus leads to inflammation that prompts fatigue.
The findings show that patients who develop CFS had elevated levels of two molecules, called interleukin-6 and interleukin-10, that cause inflammation.
These are also higher than normal in severely ill coronavirus patients.
Dr Frances Williams from King’s College London wrote in The Conversation that this suggests activation of the immune system may promote inflammation that leads to fatigue.
Calls have been made for greater research into so-called post-COVID syndrome, with some scientists questioning whether it is a condition in its own right.
Additional reporting by Alexandra Thompson.