The omicron variant’s family tree has grown substantially over the last year. The brood now encompasses a subvariant soup with alphanumeric names such as BA.2, BA.5 and BF.7. The U.S. Centers for Disease Control and Prevention estimates that two versions — BQ.1 and BQ.1.1 — caused just over half of new infections in the United States during the week ending January 7.
Now, a newcomer dubbed XBB.1.5 seems poised for a rise to dominance. According to CDC estimates, it accounts for more than 80 percent of new cases in parts of the northeastern United States. For the week ending January 14, it was responsible for 43 percent of new cases across the country.
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But while previous variants such as alpha, delta and the original omicron were linked to massive surges of new infections, it’s not yet clear whether XBB.1.5 is destined for a similar path (SN: 12/21/21). Preliminary evidence suggests the subvariant, nicknamed the Kraken in some circles, is more transmissible than its predecessors. That trait, however, is a hallmark of viral evolution — successful new variants must be able to outcompete their siblings (SN: 5/26/20).
For now, experts at the World Health Organization are keeping a close eye on XBB.1.5. But it’s too early to say whether it might take over the globe. Most cases currently come from the United States, the United Kingdom and Denmark.
Science News spoke with infe …