Almost one in seven people who test positive for Covid-19 are still suffering symptoms three months later, according to new figures from the UK.
The largest study of its kind on long Covid from Britain's Office for National Statistics (ONS) found people with coronavirus are significantly more likely than the general population to report ongoing issues, which can include muscle pain and fatigue.
Among a sample of more than 20,000 people who tested positive for Covid-19 between April last year and March this year, 13.7 per cent continued to experience symptoms for at least 12 weeks.
This was eight times higher than in a control group of people who are unlikely to have had Covid-19, the ONS said.
Of those who tested positive, a fifth (21 per cent) still had coronavirus symptoms five weeks after their test.
Women were more likely than men to report long Covid at the 12-week point - with 14.7 per cent doing so compared with 12.7 per cent of men.
Prevalence of long Covid was also highest among those aged 25 to 34 (18.2 per cent) than other age groups.
From a larger sample of people with and without Covid tests, the ONS estimated that 1.1 million people in private households in the UK experienced long Covid in the four weeks to March 6.
Of these people, an estimated 697,000 first had Covid-19 - or suspected they had Covid-19 - at least 12 weeks previously, while 70,000 first had the virus or suspected they had the virus at least one year ago.
Long Covid was estimated to be adversely affecting the day-to-day activities of 674,000 people, with 196,000 reporting that their ability to undertake day-to-day activities had been limited a lot.
Of those self-reporting long Covid, those aged 35 to 69 were most affected, as were women, people living in the most deprived areas, those working in health or social care and those with a pre-existing condition.
Health and social care workers experienced the highest prevalence rates of self-reported long Covid among employment groups (3.6 per cent and 3.1 per cent respectively), followed by those working in personal services (2.8 per cent), civil service or local government (2.7 per cent) and teaching and education (2.5 per cent).
For people living in the most deprived areas the rate was estimated at 2.1 per cent, while for those in the least deprived areas it was 1.4 per cent.
Britain's Health Secretary Matt Hancock said he is "very worried" about the impact of long Covid and that the British government is investing more in tackling and understanding the condition.
"We can see the impact in these new statistics shown today and I understand the impact it has had on hundreds of thousands of people," he told Sky News. "It's one of the many damaging problems of this virus."
Jude Diggins, interim director of nursing, policy and public affairs at the Royal College of Nursing, said long Covid "needs to be recognised as an occupational disease, with more specialist clinics to meet increasing demand" to "help nursing staff and patients alike get the support they need."
In February, the the World Health Organisation's Europe director told a briefing that the burden of long Covid "is real and it is significant".
Dr Hans Kluge said that as the pandemic had evolved, professionals and patients "have mapped a path in the dark" and stories of people with ongoing "debilitating symptoms" have emerged.
"Regrettably, some were met with disbelief, or lack of understanding," he said, adding that disability following coronavirus infection can linger for months "with severe social, economic, health and occupational consequences".
He added: "We need to listen and we need to understand. The sufferers of post-Covid conditions need to be heard if we are to understand the long-term consequences and recovery from Covid-19."