The most transmissible variant yet of the coronavirus is threatening a fresh wave of infections in the United States, even among those who have recovered from the virus fairly recently.
The subvariant of Omicron known as BA.5 is now dominant, according to federal estimates released Tuesday, and together with BA.4, another subvariant, it is fueling an outbreak of cases and hospitalizations.
"I think there's an underappreciation of what it's going to do to the country, and it already is exerting its effect," said Eric Topol, a professor of molecular medicine at Scripps Research, who has written about the subvariant.
BA.5 and BA.4, both subvariants of the Omicron variant that swept the world during the winter, are the most capable versions of the virus yet at evading immunity from previous infections and vaccines. Both variants have mutations in their spike proteins that are different enough from earlier versions of the virus that they are able to dodge some antibodies.
Waves of infection — and the subsequent immunity that comes with them — vary across countries and make for imperfect comparisons. Vaccination rates also vary. But in places where BA.4 and BA.5 have been dominant for weeks or months, the subvariants have caused increases in cases and hospitalizations, despite some population immunity from previous waves