A ‘highly infectious’ Covid strain has emerged and is already behind one in 25 cases in the UK, data suggests.
The strain — dubbed XBB.1.5 — has caused alarm in the US over its quick spread and a recent rise in hospitalisations. It is behind four in ten cases in the country, up from two a week ago.
The variant, which is a version of Omicron, has mutations that help it dodge protection from vaccination and prior infections.
Experts told MailOnline that strain is a ‘wakeup call’ and could worsen NHS crisis, which has seen the health service battered by a ‘twindemic’ of Covid and flu.
However, officials caution that there is no indication the strain causes more severe illness than earlier variants.
XBB.1.5 has gained mutations, including F486P, which help it to bypass Covid-fighting antibodies that were generated in response to vaccination or previous infection.
Another change — S486P — is thought to improve its ability to bind to cells.
Figures from the Sanger Institute, one of the UK’s largest Covid surveillance centres, shows 4 per cent of cases in the week to December 17 were caused by XBB.1.5.
It is the first time the strain has been listed on the institute’s virus dashboard, which is updated weekly.
The strain is a mutated version of Omicron XBB, which was first detected in India in August.
XBB, which is a merger of variants BJ.1 and BA.2.75, caused cases to quadruple in just one month in some nations.
Professor Lawrence Young, a virologist at Warwick University, told MailOnline that the emergence of the strain is a ‘wakeup call’ and could exacerbate the NHS crisis.