A fifth of people still have coronavirus symptoms five weeks after being infected, with half of them continuing to experience problems for at least 12 weeks, official data suggests, as concerns grow about the scale and impact of “long Covid”. Previous estimates suggested 14.5% of people in the UK had symptoms for at least four weeks, with 2.2% likely to have symptoms lasting 12 weeks or more. But new figures from the Office for National Statistics suggest ongoing symptoms could be more common than previously thought. The latest data for England, based on the Covid infection survey, which randomly samples households for coronavirus, reveals 21% of almost 8,200 participants who were followed up after testing positive still had symptoms five weeks after infection, with 9.9% reporting symptoms 12 weeks after infection. Danny Altmann, a professor of immunology at Imperial College London, said the picture was concerning. “These figures are somewhat more worrying even than many had feared. If one extrapolates to global Covid-19 cases, this means there are 5-10 million people out there with a long-term condition for which we have no current explanation and no treatment plan,” he said, adding there was no information on how long the condition lasts. “Collating the data is a first step but there’s much that needs to be done. It’s some help that dedicated clinics will roll out shortly, but until we have more insight, it will be hard to gain maximal benefit from that provision,” he added. About 11.5% of participants reported experiencing fatigue five weeks after infection, with 11.4% reporting a cough and 10.1% citing headaches. Fever, muscle aches, diarrhoea, and loss of taste and smell were among a long list of other symptoms many continued to experience. The ONS team said the data suggested more than 186,000 of the estimated 1.12 million people who were infected in England between 30 August and 23 October were still experiencing symptoms by the week beginning 22 November, and hence could potentially be classed as having “long Covid”. The study also reveals that those admitted to hospital with Covid have a higher risk of conditions including cardiovascular events – such as stroke or heart attack, diabetes, kidney disease and liver disease, than matched controls with similar demographics and pre-existing conditions. While the ONS infection survey has been collecting data since April and now covers a large number of participants, the team say only a relatively small number of people in the study who tested positive have more than 12 weeks of follow-up time. That means there is not enough data as yet to explore how common it is for symptoms to last beyond 12 weeks. However, testimonies from Covid patients suggest they can last for many months, with some who caught Covid in the first wave continuing to experience symptoms more than eight months later. Dr Claire Steves, of King’s College London, a member of the team behind the Covid symptom study app, said the figures were illuminating – and higher than their estimates. But, she said, it seemed participants in the ONS study were not asked whether the symptoms recorded only began after infection. “Therefore, people who have long-term symptoms from another cause will be included,” she said. “In our data, when we include individuals who had symptoms well before testing positive for Covid-19 we get very similar estimates to the ONS.”