What is the XFG Covid variant? Symptoms explained as cases rise in London

Covid is on the rise again in London with the highest level of cases in a year, partially driven by a new “American” strain.Latest figures released by the UK Health Security Agency (UKHSA) show that, nationally, cases have more than doubled and hospital admissions are up five-fold in the last month.The data shows that 1,374 people in Britain contracted Covid in August - but in September, this jumped 230% to 4,589.The data is more concerning when focussing on the end of the month, with cases rising nationally by almost 30% in the seven days to September 23.Number of Covid cases in London over the past 12 monthsUKHSAHow much have Covid cases increased in London?There were 258 cases in London by late September, compared to just 44 at the end of August.Hospitalisations have also risen sharply in the capital.The UKHSA data shows there were 142 Londoners in hospital with Covid at the end of July, but 289 hospitalised by the end of August, the most recent figures available.The true number of infections is almost certainly much higher, however.Number of patients in hospital with Covid in LondonUKHSAThe UKHSA figures come from NHS England’s reports from tests on patients who become very unwell with the virus, and as such not including those suffering from milder symptoms who have not been admitted to hospital or officially diagnosed.While cases are still far below their peak in January 2021 when there were more than 20,000 people in hospital across the UK, officials are urging eligible people to get their Covid jabs ahead of the winter months when cases typically rise.What is the XFG Covid variant?Many of the positive tests have been found to be a variant of XFG, also known as the Stratus or “American Covid” strain.The strain was first identified last January and has been in circulation in Europe and North America since the end of 2025.Symptoms of the strain are similar to previous variants, causing a sore throat, cough, and fever.This winter’s vaccine has been specifically designed to protect against the XFG strain and its variants.What have the experts said?The NHS has advised those who think they have any Covid strain to avoid contact with other people for five days, or three days for those under 18.People who have a positive test should avoid meeting people with weakened immune systems for 10 days after the day they took the test.Case rates per 100,000 population in the rolling 7-day periodUKHSADr Alex Allen, Consultant Epidemiologist from the UKHSA, told BBC Radio London: “Over the last month or two we have seen increases in COVID activity, both in terms of case numbers and hospital admissions.Read More“COVID continues to circulate in the UK on a regular basis. The last major peak was around a year ago, so this is roughly the time of year when we would expect activity to increase again.“As we enter winter, changes in weather and people spending more time indoors contribute to the spread of respiratory viruses. In addition, immunity gained from previous infections and vaccinations can wane over time.“Overall, the increases we’re seeing are broadly in line with what we would expect.”