COVID in US: Omicron cases jump to 18pc

The highly-contagious Omicron subvariant XBB has surged to more than 50 percent of Covid-19 cases in the northeastern United States and risks spreading fast as millions of Americans begin holiday travel on Friday.

In the week ended Dec. 24, XBB was estimated to account for 18.3% of the Covid-19 cases in the United States, up from 11.2 percent in the previous week, according to the US Centers for Disease Control and Prevention on Friday.

The subvariant is currently dominant in the Northeast, but accounts for fewer than 10 percent of infections in many other parts of the country, the CDC said.