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A new Covid variant called XFG and nicknamed "Stratus" has become dominant in the UK, as the virus continues to mutate and change over time. Experts are closely monitoring all mutations ahead of the challenging winter months when viruses will contribute to intense strain on the NHS. So what do we know about XFG and how worried should we be?

Latest data published by the UK Health Security Agency (UKHSA) confirmed that XFG accounts for the largest proportion of Covid cases, but infections were described as "stable and at low levels".

Professor Azeem Majeed, an expert in primary care and public health at Imperial College London, told the Express: "XFG has become dominant in England, accounting for around 40% of sequenced cases as of mid-2025, rising to over 60% in recent weeks. Although it may spread more easily than some other variants, there is currently no evidence that XFG is more dangerous."

The World Health Organisation (WHO) designated XFG a "variant under monitoring" in July as it began to account for a rising proportion of infections globally.

It said at the time that the public health risk posed by the variant was "low" and there was no indication that this strain leads to more severe illness or deaths than others in circulation.

Prof Majeed said: "WHO and UKHSA assessments classify the public health risk as low, with no reports of increased severity, hospitalisations, or deaths compared to prior variants."

All viruses change and mutate over time. These mutations can have no effect but can if they can change the virus's properties in ways that help it spread more easily, cause more serious disease, or evade immunity generated by previous vaccination.

Reports this summer suggested XFG may be linked to a particular symptom - hoarseness and a scratchy or raspy voice. However, Prof Majeed said the symptoms appeared "typical of a Covid-19 infection".

He added: "Current vaccines are likely to help reduce the risk of severe outcomes such as hospital admission or death."

Typical Covid symptoms include a high temperature or shivering, a new, continuous cough, a loss or change to sense of smell or taste, shortness of breath, aches and tiredness.

Hospital admissions for Covid had risen very slightly from 1.90 per 100,000 population to 2.05 per 100,000 in the most recent week for which UKHSA data is available. But this remained a low level compared to peak periods in the past.

Admissions are expected to rise further in winter as people spend more time indoors, where viruses can spread easily.

The NHS Covid vaccine rollout is expected to begin on October 1, with appointments now available to book through the NHS National Booking System.

Dr Amanda Doyle, national director for primary care and community services at NHS England, said: "The threat from getting seriously ill from flu and Covid-19 is all too real and each year we see hundreds of thousands of people hospitalised due to these nasty viruses - especially across the winter months.

"Vaccination is our best defence against these viruses and can be lifesaving."