By Fiona Callingham
A new Covid strain might trigger another “surge of infections, an expert has warned. The XFG variants, alternatively referred to as “Stratus”, have already established themselves as the predominant strain across the UK. Latest data from the UK Health Security Agency (UKHSA) reveals that the XFG strain, dubbed Stratus, is rapidly spreading throughout England, whilst the World Health Organisation (WHO) has highlighted its “rapidly growing” global presence. During May, the Stratus variant accounted for 10 per cent of Covid-19 cases in England. Currently, the XFG and its sub-variant, XFG.3, are behind roughly 40 per cent of infections, based on UKHSA data. Between May 26 and June 8, 28.9 per cent of cases were classified as the XFG. 3 variant, whilst 11.4 per cent were linked to XFG. According to the Manchester Evening News , both fall under the Stratus category, with XFG being the parent strain and XFG. 3 its descendant. Dr Alex Allen, consultant epidemiologist at UKHSA, said: “It is normal for viruses to mutate and change over time. “UKHSA is monitoring all available data relating to SARS-CoV-2 variants in the UK and abroad, and we continue to publish our findings in our regular Flu and COVID-19 surveillance reports. Based on the available information so far, there is no evidence to suggest that the XFG and XFG.3 variants cause more severe disease than previous variants, or that the vaccines in current use will be less effective against them.” This development comes hot on the heels of the WHO’s announcement regarding a fresh “more transmissible” strain called Nimbus, or NB. 1.8.1, which remains under scrutiny. Recent data reveals that the Nimbus variant of Covid is experiencing a decline across the UK, now representing merely 7.19 per cent of cases in England under the designation NB. 1.8.1. The Stratus variant has overtaken Nimbus to emerge as the dominant strain in England. Virologist Professor Lawrence Young from Warwick University told the MailOnline about the concerning surge of the Stratus variant and its sub-lineages XFG and XFG. 3: “The increased competitiveness of XFG and XFG.3 is likely due to new spike mutations which make these variants more able to evade the immune response.” He raised the alarm regarding diminishing immunity amongst the population, stemming from reduced uptake of the spring booster jab and falling Covid infection rates of late. Prof Young cautioned: “This could lead to a new wave of infection but it’s difficult to predict the extent of this wave.” Speaking to Cosmopolitan UK about the Stratus variant’s characteristics, Dr Kaywaan Khan, Harley Street GP and Founder of Hannah London Clinic, expressed his worries: “Unlike other variants, Stratus has certain mutations in the spike protein which could help it evade antibodies developed from prior infections or vaccinations.” Dr Khan characterised the Stratus strain as a derivative of the Omicron variant, recognised for its exceptional contagiousness and initially identified in November 2021. Examining the circumstances in May 2025, data indicates that XFG represents approximately 25 per cent of worldwide Covid infections. Dr Khan observed: “Despite this, it is important to mention that Stratus seems to be no worse than earlier Omicron variants in terms of illness, hospitalisations, or deaths.” The World Health Organisation (WHO) has warned that the XFG strain is spreading rapidly across the globe. The body documented that infections escalated dramatically within a month, rising from seven per cent of international cases to 23 per cent by June 1. However, WHO has assessed this variant’s risk level as “low”. The organisation maintains there is presently no evidence suggesting XFG poses greater health dangers compared to previous iterations of the virus. The newest COVID-19 variants, often colloquially dubbed “Frankenstein” variants, typically manifest symptoms similar to earlier Omicron subvariants. These signs commonly encompass upper respiratory difficulties including fever, cough, sore throat, runny nose, and sneezing. Additional manifestations such as exhaustion, headache, muscle aches, and reduced appetite are frequently documented too. It’s noteworthy that the previously characteristic symptom of losing one’s sense of smell or taste seems to occur less commonly with Omicron infections.