U.S. health regulators on Friday estimated that BQ.1 and closely related BQ.1.1 accounted for 16.6 percent of coronavirus variants in the country, nearly doubling from last week, while Europe expects them to become the dominant variants in a month.

The European Center for Disease Prevention and Control said the variants are likely to drive up cases in the coming weeks to months in the European region.

The two variants are descendants of Omicron's BA.5 subvariant, which is the dominant form of the coronavirus in the United States. Regulators in Europe and the U.S. have recently authorized vaccine boosters that target it.

There is no evidence yet that BQ.1 is linked with increased severity compared with the circulating Omicron variants BA.4 and BA.5, European officials said, but warned it may evade some immune protection, citing laboratory studies in Asia.

"These variants (BQ.1 and BQ.1.1) can quite possibly lead to a very bad surge of illness this winter in the U.S. as it's already starting to happen in Europe and the UK," said Gregory Poland, a virologist and vaccine researcher at Mayo Clinic.

The World Health Organization (WHO) this week said BQ.1.1 is circulating in at least 29 countries.

New threat

A new Omicron sub-variant, known as the XBB, which is a predominant variant in Singapore, now has been identified in 26 countries, the WHO said on Wednesday without specifying which countries.

"There are over 300 subvariants of Omicron. I think the one that is concerning right now is XBB which is a recombinant virus. We had seen some recombinant viruses before," The Economic Times reported on Friday citing WHO Chief Scientist Soumya Swaminathan as saying.

"It is very immune evasive which means, it can overcome the antibodies. So slightly we may see another wave of infections in some countries because of XBB," she said. 

Read more:

XBB variant: How dangerous is the newest COVID-19 strain?

(With input from Reuters)

(Cover via CFP)