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The Omicron sub-variant of COVID known as BA.2 accounts for nearly a quarter of all new sequenced U.S. cases, according to estimates from the Centers for Disease Control and Prevention (CDC).
According to CDC data released yesterday, BA.2 was projected to have been identified in 23.1 percent of new sequenced COVID samples between March 6 and March 12.
This marks a sharp increase from the previous week, where BA.2 was estimated to have been found in 13.7 percent of samples, and in 7.1 percent samples the week before that.
If current trends continue BA.2 is on its way to overtaking other types of Omicron in the U.S., including the BA.1 sub-type that has generally been the globally dominant version up to now.
The CDC data also showed BA.2 hotspots within the country and the prevalence of the sub-variant in ten different regions, each encompassing multiple states.
BA.2 appears most prevalent in region 2, which includes New Jersey, New York, Puerto Rico, and the Virgin Islands. There, it was found in 39 percent of samples up to March 12.
Another hotspot was region 1, which includes Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. There, BA.2 was found in 38.6 percent of samples.
Prevalence in all other regions was below 30 percent and as low as 12.4 percent in region 4—Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee.
It should be noted that the above data is based on the Nowcast model, which provides estimates of circulating variants. Non-estimated figures are usually made available within a couple of weeks of the estimates being released.
Cases of BA.2 are also increasing elsewhere. Data from the U.K. Health Security Agency (HSA) on March 11 showed that, between February 27 to March 6, 68.6 percent of sequences cases were BA.2 while 31.1 percent were BA.1, suggesting BA.2 had become dominant.
BA.2 is a sub-type of the Omicron variant that has been found to have a higher growth rate than the previously dominant BA.1. It has been the subject of ongoing study this year after it was reported to be increasing as a proportion of cases in a number of countries.
The U.K.'s March 11 HSA data showed that risk of hospitalization following infection with BA.2 does not appear to be any higher than after a BA.1 infection so far.
One key characteristic of BA.2 is its ability to reinfect people who have already had BA.1, meaning they could get Omicron twice. Such cases have been identified, but they remain relatively rare so far.
