“This virus has probably got tricks we haven’t seen yet,” virologist Robert F. Garry of Tulane University said. “We know it’s probably not quite as infectious as measles yet, but it’s creeping up there, for sure.”

The latest member of the rogue’s gallery of variants and subvariants is the ungainly named BA.2.12.1, part of the omicron gang. Preliminary research suggests it is about 25 percent more transmissible than the BA.2 subvariant that is currently dominant nationally, according to the Centers for Disease Control and Prevention. The CDC said the subvariant has rapidly spread in the Northeast in particular, where it accounts for the majority of new infections.

“We have a very, very contagious variant out there. It is going to be hard to ensure that no one gets covid in America. That’s not even a policy goal,” President Biden’s new covid-19 coordinator, Ashish Jha, said in his inaugural news briefing Tuesday.