Katherine J. Wu writes:

After months and months of SARS-CoV-2 subvariant soup, one ingredient has emerged in the United States with a flavor pungent enough to overwhelm the rest: XBB.1.5, an Omicron offshoot that now accounts for an estimated 75 percent of cases in the Northeast. A crafty dodger of antibodies that is able to grip extra tightly onto the surface of our cells, XBB.1.5 is now officially the country’s fastest-spreading coronavirus subvariant. In the last week of December alone, it zoomed from 20 percent of estimated infections nationwide to 40 percent; soon, it’s expected to be all that’s left, or at least very close. “That’s the big thing everybody looks for—how quickly it takes over from existing variants,” says Shaun Truelove, an infectious-disease modeler at Johns Hopkins University. “And that’s a really quick rise.”

All of this raises familiar worries: more illness, more long COVID, more hospitalizations, more health-care system strain. With holiday cheer and chilly temperatures crowding people indoors, and the uptake of bivalent vaccines at an abysmal low, a winter wave was already brewing in the U.S. The impending dominance of an especially speedy, immune-evasive variant, Truelove told me, could ratchet up that swell.

But the American public has heard that warning many, many, many times before—and by and large, the situation has not changed. The world has come a long way since early 2020, when it lacked vaccines and drugs to combat the coronavirus; now, with immunity from shots and past infections slathered across the planet—porous and uneven though that layer may be—the population is no longer nearly so vulnerable to COVID’s worst effects. Nor is XBB.1.5 a doomsday-caliber threat. So far, no evidence suggests that the subvariant is inherently more severe than its predecessors. When its close sibling, XBB, swamped Singapore a few months ago, pushing case counts up, hospitalizations didn’t undergo a disproportionately massive spike (though XBB.1.5 is more transmissible, and the U.S. is less well vaccinated). Compared with the original Omicron surge that pummeled the nation this time last year, “I think there’s less to be worried about,” especially for people who are up to date on their vaccines, says Mehul Suthar, a viral immunologist at Emory University who’s been studying how the immune system reacts to new variants. “My previous exposures are probably going to help against any XBB infection I have.” [Continue reading…]