Omicron subvariants BQ.1 and BQ.1.1 are now dominant in the U.S., accounting for more than 40 percent of U.S. COVID-19 cases, CDC data shows.
BQ.1 accounted for an estimated 20.1 percent of cases in the week ending Nov. 12, up from 16.1 percent the week prior. BQ.1.1, which has one additional mutation, accounts for an estimated 24.1 percent of cases.
The strains — dubbed "escape variants" for their immune evasiveness — have quickly overtaken BA.5, which had been the nation's dominant strain since early July.
The subvariants' climbing prevalence is fueling concerns of a potential winter COVID-19 surge, though most experts predict any jump in infections would be less severe than the past two winter surges.
"This time of year last year we were optimistic. We were coming out of the delta wave, and it was steadily decreasing, and we went into Thanksgiving to wake up to omicron," Jeremy Luban, MD, a physician-scientist at Amherst-based University of Massachusetts, told NPR. "So there is this sort of déjà vu feeling from last year."