Officials from the UK Health Security Agency are formally tracking the variant.

The new strain comes as the NHS deals with rising pressures over the winter period, including industrial action.

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It is expected to use extra ambulances, more beds and expand its so-called virtual wards.

Health chiefs have also called on Britons to get their flu and Covid booster jabs to reduce the risk of hospitalisation.

Dr Meaghan Kall, an epidemiologist at the UKHSA, claimed JN.1 has a weekly estimated growth rate advantage of 84.2 per cent.

Writing on social media, Dr Kall warned JN.1 “might cause a wave”, adding: “It seems likely we must now add variant pressures to the forecast of a winter Covid wave.”

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She also argued the variant is taking off faster than any other strain seen in at least eight months.

Despite some concerns, officials stress the overall number of coronavirus cases remain low.

The UKHSA does not consider JN.1 a threat and experts suggest the chance it could force another lockdown is tiny.

Immunity through vaccines and infections has reduced the threat previously posed by Covid.

However, the new variant comes amid a rise in patients suffering from norovirus, flu and RSV.

Professor Julian Redhead, NHS England's national clinical director for urgent and emergency care, said rates of all the seasonal bugs are “creeping up”.

He added: “Demand on hospitals and staff remains high.

“And as we experience more spells of cold weather and people gathering indoors for festive events and end of year celebrations, we expect to see a continued increase in winter viruses spreading in the community.”