What is post-viral fatigue syndrome, the condition affecting some COVID-19 survivors?

For many of us, becoming ill with a virus might put us on the couch for a week or two. It’s frustrating, but after recovering we can generally get back to the things we’re used to.

But for some people, contracting a viral infection can be life-altering. It can cause months, years or even a lifetime of debilitating symptoms that drastically reduce their quality of life.

These symptoms, sometimes called “post-viral fatigue syndrome”, have been reported by sufferers of many viral diseases including influenza, glandular fever, SARS, and now COVID-19.

Read more: Here's what we know so far about the long-term symptoms of COVID-19

What are the symptoms?

The World Health Organisation has classified post-viral fatigue syndrome under the section of “diseases of the nervous system”. It’s defined as:

…a complex medical condition, characterised by long-term fatigue and other symptoms. These symptoms are to such a degree that they limit a person’s ability to carry out ordinary daily activities.

Despite the word “fatigue”, the symptoms can be broader and more debilitating than simple tiredness. They can include a sore throat, aches and pains across the body, blood pressure changes, gastric upsets such as irritable bowel syndrome, headaches, sleep disturbance, depression, and dizziness. More severe neurological symptoms can also occur, including new sensitivities or allergic reactions, and burning or prickling sensations in the limbs. Many COVID-19 patients, for example, report a prolonged loss of smell and taste.

A key feature of the condition is that symptoms can suddenly worsen following only minimal physical or mental activity.

The symptoms are essentially the same as those of chronic fatigue syndrome, also called myalgic encephalomyelitis or ME, which is why the WHO places them under the same category of neurological disorders.

If you went to see a doctor, the clinical assessment for post-viral fatigue syndrome would be the same as for chronic fatigue syndrome.

However, not everybody who gets chronic fatigue syndrome has had a virus, which may explain why both terms persist. There are no current diagnostic tests for post-viral fatigue syndrome, and a diagnosis can only be made based on a series of symptoms.

Read more: What causes chronic fatigue? What we know, don’t know and suspect

It’s being reported in COVID-19 survivors

Post-viral symptoms have been reported following outbreaks of often unexplained viruses in many different countries. One of the earliest outbreaks recorded was in 1934 in California, where people infected with an unknown virus (thought to be polio) experienced “bursting headaches”, aching limbs and muscle weakness for a prolonged period. Other episodes were recorded in Iceland in 1948, and in Adelaide in 1949.

Although we’re in the early stages of understanding COVID-19, there have been many reports and some research into post-viral symptoms in sufferers.

For example, an Italian study from July found 55% of the hospitalised COVID-19 patients studied suffered at least three debilitating symptoms, two months after their apparent recovery from the initial infection. And a UK study in August estimated 10% of those with COVID-19 go on to develop post-viral symptoms.

This is not necessarily surprising, given research on other similar viruses. One Canadian study found 21 health-care workers from Toronto had post-viral symptoms for up to three years after catching SARS in 2003, and were unable to return to their usual work.

A 2006 Australian study examined 253 people from Dubbo after they caught infections including glandular fever, Q fever, and Ross River virus. It found 11% of cases went on to develop chronic post-viral symptoms that lasted at least six months.

What causes it?

The condition, alongside chronic fatigue syndrome, is poorly understood. Researchers are still trying to understand how the body is affected, and for a way to objectively diagnose it.

Any viral infection can apparently trigger the condition, if it leads to long-term complications. It can follow a bout of common influenza, the herpes HHV-6 virus, gastric ailments such as Coxsackievirus, or life-threatening conditions like COVID-19, SARS and MERS.

Another potential trigger is glandular fever, also called mononucleosis or the Epstein-Barr virus. It infects more than 90% of the world’s population, but affects mostly people aged 18-25. For some, catching the commonly known “kissing disease” can be the start of a chronic and debilitating illness.

While a virus might be the trigger, scientists don’t yet know the actual cause. One theory is that post-viral fatigue syndrome may result from an overreaction of the body’s immune system, inducing widespread inflammation. This is highlighted by elevated levels of immune messengers called cytokines, which can cross the blood-brain barrier and potentially cause long-term toxic brain changes affecting the whole nervous system.

Almost every part of the body is affected by a virus, and some lay dorment in our system and can be reactivated when our immune system is weakened. A good example of this is shingles, which is a reactivation of the chickenpox virus.

Researchers are also focusing on whether there’s an autoimmune component to the disease, where our immune system provides a rapid response which can inadvertently damage healthy tissue, affecting all of the body’s systems such as the heart, digestion, and may even cause diabetes.

Others are looking into why mitochondria, the structures that generate energy within cells, are affected and may result in fatigue. Researchers are also working toward finding “biomarkers” in the body — objective indicators that can help with diagnosing the condition — though no reliable ones have been located yet.

Read more: Chronic fatigue syndrome: new evidence of biological causes

How is it treated?

Sadly, there is no specific medication or speedy treatment for post-viral fatigue or chronic fatigue syndrome. Treatment options include using a variety of health professionals with diverse approaches, typically tailored to the individual.

The most effective current treatment is total rest. This means relaxing as much as possible, with no mental stimulation such as television or reading. People who have experienced the condition talk about lying in a darkened room for long periods to promote mental and physical rest.

Other treatments focus on specific symptoms. If pain is the main feature, a rheumatologist might be used, who specialises in managing diseases of the joints, bones and muscles. Psychological treatments such as cognitive behavioural therapy or mindfulness might also help relieve some symptoms.

If you are supporting someone with the condition, it’s important to respect their need for rest and help them through the anxiety of endless tests in their search for answers.

Many patients, particularly with chronic fatigue syndrome, say they aren’t believed and are made to feel like they’re faking their symptoms by both friends and doctors. The shame and stigma associated with it can be crushing and hurtful and may even result in depression.

And, the experience of getting a virus during a pandemic is stressful, causing anxiety and even PTSD for some.