The effects of "long Covid" could turn out to be a bigger public health problem than excess deaths, one of Britain's leading experts has warned.
Professor Tim Spector, the scientist behind Britain's symptom-tracking app, warned that the virus behaves like an autoimmune disease in some sufferers, affecting multiple parts of the body.
Those suffering with so-called "long Covid" have reported breathlessness, chronic fatigue and brain fog - months after initially falling ill with the virus.
Spector, Professor of Genetic Epidemiology at King's College London, said their research had found that the effects of the virus lingered for a long time in significant numbers of people.
Researchers from King's College London and health-science company ZOE tracked data from more than 4 million people.
They found that one in 10 sufferers had symptoms of "long Covid" for a month, with 1 in 50 still suffering at least three months later.
"Long Covid" was found to be most common in those of working age, with a median age of 45 among those afflicted, and cases rare in those above the age of 65 and below the age of 18. Women were more likely than men to be affected.
A report from the Tony Blair Institute for Global Change on Sunday (Monday NZ time) urged the UK government to do more to highlight the issue.
The authors of the paper, titled Long Covid: Reviewing the Science and Assessing the Risk, say they believe awareness campaigns "would help drive compliance with containment measures such as the use of masks".
In the report's foreword, Spector said that in the first few months of the pandemic, little attention was paid to the infected population who were not sick enough to go to hospital, who made up 99 per cent of cases.
He said it turned out that Covid-19 was not just a bad flu, but in many people it behaved more like an autoimmune disease, affecting multiple systems in the body.
Researchers learned that "a great many people didn't get better after two weeks as expected", Spector said, adding: "We kept following them and found out that a significant number still had problems after months.
"This is the other side of Covid: the long-haulers that could turn out to be a bigger public-health problem than excess deaths from Covid-19, which mainly affect the susceptible elderly."