Scientists have called for people in the UK to wear face masks again amid a worrying new COVID-19 variant “mutation.”

They expressed concern over a subvariant of Omicron, “Eris,” which now accounts for one in 10 cases in the UK.

The number of people diagnosed with the virus jumped from an estimated 3.3 per 100,000 to 7.2 in the space of less than a month, the Mirror reported Wednesday.

A new sub-strain referred to as "BA.6” has also caused worry, although it has only been found in Denmark and Israel for now.

Trisha Greenhalgh, a primary healthcare expert at the University of Oxford, urged people to wear masks again.

"My various science WhatsApp groups are buzzing. Genetic lineage clips and diagrams flying back and forth. I understand little of the detail, but it looks like it's once again time to MASK UP," she said on X, formerly known as Twitter.

Prof. Christina Pagel from University College London also said the sub-strain had the potential to cause "a big wave."

The variant has a "LOT of new mutations that makes it (very) different to previous Omicron strains," she said on X.

Additionally, in an opinion piece published this week in the British Medical Journal, Pagel said "it is reasonably certain that we have entered another COVID-19 wave."