A mutant covid strain first spotted in the UK back in October is now being blamed for one in every 25 infections across the country.
The XBB 1.5 variant is a type of Omicron and is said to be more infectious as it spreads quickly and appears to evade people's vaccine protection.
Neither of the Omicron strains BQ.1 or XBB have been listed as variants of concern by the UK Health Security Agency.
The latest figures - for the week to Saturday, December 17 - from Cambridge's Sanger Institute show that four per cent of all UK covid cases were of the XBB 1.5 variant.
XBB 1.5 is a mutated version of Omicron XBB, which was first detected in India in August.
This is the first time the XBB 1.5 variant has made the Sanger Institute's list of variants, with BA.5 still responsible for more than 70% of infections.
- BA.5 71.3%
- BA.2 17%
- XXB 6.7%
- XXB 1.5 4%
- BA.4 0.4%
- B.1.1.59 0.4%
Dr Meera Chand, director of clinical and emerging infection at the UKHSA told the Mirror: “It is not unexpected to see new variants of SARS-CoV-2 emerge.
"Neither BQ.1 nor XBB have been designated as Variants of Concern and UKHSA is monitoring the situation closely, as always.
“Vaccination remains our best defence against future COVID-19 waves, so it is still as important as ever that people come take up all the doses for which they are eligible as soon as possible.”
Professor Lawrence Young, a virologist at Warwick University, said the new strain is a 'wakeup call' and could exacerbate the crisis in the NHS.
Prof Lawrence told the Mail: "The XBB.1.5 variant is highly infectious and is driving increased hospital admissions in New York, particularly among the elderly, waning immunity, more indoor mixing because of the cold weather and lack of other mitigations, such as wearing face masks, are also contributing to this surge of infection in the US.
"We don’t know how this variant is going to behave in the UK in a population that has been previously exposed to other Omicron variants and where many of the over 50s have had booster shots with a bivalent vaccine.
"Nevertheless, this is a wakeup call — a sharp reminder that we can’t be complacent about Covid. The threat of XBB.1.5 and other Covid variants further exacerbating the current NHS crisis stresses the need for us to remain vigilant."
