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The omicron surge is continuing to lose steam in the U.S. — new cases of COVID-19 are a small fraction of what they were in early February — but it's possible that this improvement could be interrupted. Experts are tracking a subvariant of omicron that is behind an uptick of new infections in a handful of countries, as well as the majority of COVID-19 cases in the U.S.
Its official name is BA.2, but some scientists have dubbed the subvariant “stealth omicron” because of a mutation that makes it show up differently than its sibling strain on lab tests. Experts point out that the “stealth” in the name doesn’t imply the subvariant evades detection by lab-based and at-home tests — it doesn’t — but rather that test results don’t mimic the original omicron variant precisely.
Here’s what we know so far about BA.2 and its impact on the state of the pandemic in the U.S.
Its presence is growing
The subvariant was first identified around the same time as omicron, also known as BA.1, “but we didn’t really see a lot of cases of it,” said Egon Ozer, M.D., an assistant professor at Northwestern’s Feinberg School of Medicine and director of the Center for Pathogen Genomics and Microbial Evolution in the Havey Institute for Global Health. “It really was the first version, BA.1, that spread around the globe and caused surges.”
Cases of COVID-19 caused by BA.2, however, are on the rise in a handful of countries, including the U.S., where it now accounts for more than 70 percent of all new COVID-19 infections, up from about 1.5 percent in early February.
BA.2 is more contagious
There is “growing evidence” that BA.2 is more transmissible, or contagious, than the original omicron variant, Mark McClellan, M.D., director of the Duke-Margolis Center for Health Policy, said during a media briefing, pointing to places in Europe “where BA.2 has now taken over much of the continuing caseload.”
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