WHO: The New Subvariant of COVID-19 is the Most Contagious so far

The subvariant of the coronavirus: Omicron XBB.1.5, which in just a few weeks has become dominant in the United States, may cause a new wave, a representative of the World Health Organization told reporters.

"We are concerned about its transmissibility, particularly in some countries in Europe and the northeastern US, where XBB.1.5 has rapidly displaced other circulating subvariants," said Maria Van Kerkhove, technical lead for COVID-19 at the World Health Organization.

However, health officials are not sure if this will lead to more hospitalizations or deaths.

The subvariant has been found in 29 countries, but it may be circulating in many more, Van Kerkhove said.

In the US, the subvariant has increased from 4% of sequenced cases to 40% in just a few weeks, the White House's coordinator for the COVID crisis response, Ashish Jha, said on Twitter. But the WHO has yet to officially announce whether XBB.1.5 is more dangerous than other circulating subvariants.

Van Kerkhove, said the increase in hospitalizations in North-Eastern Europe could not yet be attributed to XBB.1.5, as other respiratory illnesses, including influenza, could be partly to blame.

Jha cautioned that Americans' immunity to XBB.1.5 is "probably not great" if the previous infection was before July or if they did not receive the bivalent vaccine that became available in September. He advised people to get a bivalent vaccine, to get tested before attending large gatherings or meeting elderly and immunocompromised people, and to wear a high-quality mask in crowded indoor spaces.

The WHO is working on an analysis of the severity of the new subvariant, which it will publish in the coming days, Van Kerkhove said.