What we know: Public health officials have detected the strain in 29 countries, but it could be circulating in many more countries, Van Kerkhove said.
In the US, the subvariant rose from 4 percent of sequenced cases to 40 percent in just a few weeks, White House Covid-19 Response Coordinator Ashish Jha tweeted Wednesday.
But WHO does not yet know if XBB.1.5 is more severe than other circulating subvariants.
The United States is suffering far less from Covid than it was a year ago. Death rates were about seven times higher this time last year, and hospitalizations were almost three times higher. However, both categories have been lower at different times of the pandemic, and hospitalizations in New England, where XBB.1.5 is spreading rapidly, are increasing and are at about 40 percent of last year’s levels.
Van Kerkhove said the increase in hospitalizations in the North East cannot yet be attributed to XBB.1.5 as other respiratory illnesses, including influenza, could be partly to blame.
What’s next: Jha warned that Americans’ immunity to XBB.1.5 “is unlikely to be high” if a previous infection occurred before July or if they did not receive the bivalent vaccine available in September.
He advised people to get their bivalent booster, test themselves before large gatherings or before meeting the elderly or immunocompromised, and wear a quality mask in crowded indoor spaces.
Covid tests and antiviral pills Paxlovid and Molnupiravir ‘should work fine from what we know’ Jha tweeted.
The WHO is working on an analysis of the severity of the new strain, which it will publish in the coming days, Van Kerkhove said.