A new Covid strain dubbed "American Covid" is now responsible for more than half of all positive tests in the UK, with cases surging by around 230% last month. The variant, officially called XFG or Stratus, originated in North America and has become dominant in the country.
Latest figures show 4,589 Covid cases were recorded in September, up from 1,374 in August. Hospital admissions also rose sharply, from 950 in August to 4,939 in September. The percentage of tests in hospitals that came back positive for Covid increased from 5.9% to 7.0% in the seven days leading up to September 30, according to figures from the UK Health Security Agency (UKHSA).
Symptoms to watch for
Claire Nevinson, superintendent pharmacist at Boots, explained the differences between cold, flu and Covid symptoms. She told the Mirror: "Common symptoms of both cold and flu include a sore throat, blocked or runny nose, sneezing and coughing. Cold symptoms tend to be milder and come on gradually. People usually start to feel better within a week or two."
"In contrast, flu symptoms tend to start more suddenly, be more severe and last longer. Common flu symptoms include a fever, aching muscles and chills."
"The main symptoms of Covid are a high temperature, a new, continuous cough and loss or change to your sense of taste or smell, but people can also get other symptoms which are very similar to colds and flu."
XFG's unique sign
The most common symptoms of the XFG strain are congestion, cough, fever, headache, runny nose, muscle aches, and a sore, hoarse throat. Experts say a scratchy throat that makes your voice croaky is the most unique symptom distinguishing XFG from other strains.
Claire added that while new variants this year are starting to circulate, there is little evidence so far to suggest they cause widely different symptoms from other variants.
XFG was first detected in Southeast Asia in 2025 before becoming dominant in the US. Mutations are thought to have made XFG more infectious than previous strains. Though the variant may have greater transmissibility, which, along with seasonal patterns, may be contributing to rising cases, there's no evidence to suggest it causes more severe illness.
