As many as 1 in every 10 COVID-19 patients could end up with symptoms lasting for longer than three months, with sufferers around the world terming this ‘long COVID’.


Researchers believe that these symptoms are the ‘after-effects’ of the virus, due to damage caused to the organs, immune and nervous systems. People who have been ill enough with COVID-19 to be hospitalised are more likely to need an extended recovery time than those who weren’t as badly affected, but it seems long COVID can strike anyone, of all ages and backgrounds.

We already know that there are viruses that can cause symptoms for weeks, months or years post-infection. Some long-term illness, such as myalgic encephalomyelitis (ME) and chronic fatigue syndrome, are thought to be post-viral, so it would make sense that COVID could also cause long-term problems.

Dr Matthew Knight, a specialist in respiratory medicine, has seen patients with ME in his clinic. These patients, he says, clearly show a process of deterioration over the course of many months and years. Now, he is seeing people visit the hospital with extreme fatigue, months after getting COVID-19. Will they have that picture of long-term ill health, too?

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Patients with COVID symptoms seem to fall into three cohorts, Knight says. He researched the condition with professor of primary health care Prof Trish Greenhalgh, and respiratory physiotherapist Maria Buxton.

Patients with acute COVID are those who are between day 1 and day 21 of symptoms. Most patients fall into this category, but there will be some – perhaps up to 20 per cent of all COVID-19 patients, according to the few studies currently published – who have symptoms for at least 12 weeks.

Those who have symptoms between weeks 3 and 12 are being called ‘post-acute COVID patients’. “This describes the constellation of symptoms between these weeks, which in the vast majority will resolve themselves,” says Knight.

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“Breathlessness, fatigue, cough, headache, diarrhoea, skin rashes and low mood are all symptoms in that phase that we would expect to gradually improve.” It’s unclear whether these people are still infectious.

Chronic COVID, or long COVID as it’s now widely known, is when those symptoms are present beyond 12 weeks. “Early evidence and early clinical experience seems to suggest that those symptoms won’t just disappear, or certainly not rapidly,” explains Knight.

It’s hard to know how common long COVID is. Knight says that the best figures have come from the COVID-19 symptom tracker app, which suggest that somewhere between 1 and 10 per cent of people still have symptoms at 10 to 12 weeks. At the time of writing, 530,000 people in the UK have contracted COVID-19. That means anywhere between 5,000 to 50,000 patients could be suffering with long COVID.

“We, and a number of others, have come to the conclusion that 60,000 is a good, educated guess,” says Knight. “That figure is at least the minimum that we should be planning for, [and] that we should be preparing to offer services for and rehabilitation. We shouldn’t overestimate the size of the problem. It’s not that everyone with COVID is going to have this. But it’s more than just a rarity. It’s enough people to justify serious study and review.”

So, what do scientists know about who is and who isn’t likely to suffer with symptoms more than 12 weeks after diagnosis with COVID-19? Very little, it seems, as the focus until recently has – rightly so – been on treatments and vaccines. However, research does seem to suggest that having a coexisting illness makes you more likely to get long COVID. But it can and does occur in otherwise healthy people, of all ages.

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Of those who have long COVID, there seem to be two types. “There are those that have got demonstrable, organic pathology. Scarring on their lungs, damaged cardiac muscle or neurological damage. Those patients seem to be the minority, certainly in my clinical practice based in Watford,” says Knight.

Then there are the long COVID patients who report fatigue as the predominant symptom, but also breathlessness, joint pain, diarrhoea and more. “These patients have got more normal X-rays, normal CT scans, normal lung function tests,” says Knight. “For them, no one really knows what the cause of [their symptoms] is.”

There is expertise and treatment in place for damaged hearts and lungs, but for fatigue-predominant patients, there is no such framework.


“I’ve spoken to colleagues and doctors who’ve had COVID […] They’re three, four or five months down the line, and speak about a profound exhaustion. These are real symptoms people are describing, and they need to be taken seriously,” says Knight.

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Amy ArthurEditorial Assistant, BBC Science Focus

Amy is the Editorial Assistant at BBC Science Focus. Her BA degree specialised in science publishing and she has been working as a journalist since graduating in 2018. In 2020, Amy was named Editorial Assistant of the Year by the British Society of Magazine Editors. She looks after all things books, culture and media. Her interests range from natural history and wildlife, to women in STEM and accessibility tech.