The XFG strain of Covid, known as Stratus, has quickly become one of the most dominant variants in the UK.
An expert has warned that a new variant of Covid could cause another “wave of infection”. The XFG variants, which are also known as “Stratus”, have already become the most dominant variant in the UK.
The most recent figures from the UK Health Security Agency (UKHSA) indicate that the XFG strain, known as Stratus, is swiftly proliferating across England, with the World Health Organisation (WHO) alerting to its “rapidly growing” presence worldwide.
As of May, the Stratus variant constituted 10 per cent of Covid-19 cases in England. Presently, the XFG and its derivative, XFG.3, are responsible for approximately 40 per cent of infections, according to UKHSA statistics.
In the period spanning May 26 to June 8, 28.9 per cent of cases were identified as the XFG. 3 variant, while 11.4 per cent were attributed to XFG. As reported by the Manchester Evening News, both belong to the Stratus family, with XFG being the original and XFG. 3 its offshoot.
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 update follows closely on the heels of the WHO’s disclosure of a new “more transmissible” variant named Nimbus, or NB. 1.8.1, which is also under observation.
The latest figures indicate that the Nimbus strain of Covid is on a downward trend in the UK, now accounting for just 7.19 per cent of cases in England under classification NB. 1.8.1. The Stratus variant has surpassed Nimbus to become the most prevalent variant in England.
Virologist Professor Lawrence Young of Warwick University revealed to MailOnline the worrying rise of the Stratus variant and its forms 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.”
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He sounded an alarm over waning immunity among the public, as a result of declining uptake of the spring booster vaccination and receding Covid infection numbers recently. Prof Young warned: “This could lead to a new wave of infection but it’s difficult to predict the extent of this wave.”
Expressing concerns about the behaviour of the Stratus variant to Cosmopolitan UK, Dr Kaywaan Khan, Harley Street GP and Founder of Hannah London Clinic, said: “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 described the Stratus strain as an offshoot of the Omicron variant, known for its high transmissibility and first detected in November 2021. As we look at the situation in May 2025, reports show that XFG constitutes roughly 25 per cent of the global Covid case count.
Dr Khan remarked: “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 cautioned that the XFG strain is proliferating swiftly on a global scale. The organisation reported that cases surged within a month, from accounting for seven per cent of worldwide instances to reaching 23 per cent as of June 1.
Nevertheless, WHO has evaluated the threat level of this variant as “low”. It maintains that there is no current evidence indicating that XFG presents additional health risks relative to prior variants of the virus.
Symptoms
The most recent COVID-19 variants, frequently casually referred to as “Frankenstein” variants, usually present with symptoms akin to previous Omicron subvariants. Such symptoms commonly include upper respiratory tract problems such as fever, cough, sore throat, runny nose, and sneezing.
Further symptoms like fatigue, headache, muscle pains, and decreased appetite are typically reported as well. It’s worth mentioning that the once distinctive symptom of loss of smell or taste appears to be less prevalent with Omicron infections.