The CDC most recently said BA.2 made up 23.1% of cases for the week ending March 12.
The omicron subvariant BA.2 is continuing to gain ground in the U.S., according to Covid-19 tests sequenced over the last two weeks.
Helix, a San Diego-based genomics firm, has been watching the BA.2 variant since it first popped up in the U.S. in early January. Although it was initially slow to take hold, Helix now estimates that 50% to 70% of all Covid cases nationwide are BA.2.
Will Lee, Helix's chief science officer, said this type of surveillance is essential and can help arm the U.S. health care system against future variants.
Data from the U.K. - where BA.2 has already caused cases to spike - show the country's rise in infections began around the same time that BA.2 surpassed the 50% mark of overall cases. So far, the variant appears to be no more severe than the initial omicron strain, but there's concern about its ability to reinfect people and its links to long Covid.
Cases are still dropping overall in the U.S., but some health experts are worried that decline won't last for long. Already, cases are beginning to climb in New York City, where BA.2 accounts for a larger share of cases than in other parts of the country, according to data from the Centers for Disease Control and Prevention.
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NOW is the time to get it. Here's why: Covid cases in NYC over past week (7-day avg) * Sun 647 * Mon 662 * Tue 815 * Wed 882 * Thu 905 * Fri 900 * Today 1,048https://t.co/vpCxAcY4FU
The CDC has yet to update its variant surveillance data for this past week, but the agency has reported BA.2 nearly doubling in prevalence each week since early February. The CDC most recently said BA.2 made up 23.1% of cases for the week ending March 12.
Variant surveillance at Helix is funded by the CDC and its sequencing data is one of many the agency takes into account when creating its Nowcast estimates each week. According to Helix, the firm is able to process up to 150,000 Covid-19 tests per day across the country.
Lee, the Helix scientist, said that although he expects cases to rise in coming weeks, he does not anticipate as significant a spike as was caused by the first omicron strain. That's due to the immunity people have already built up through vaccines and prior infections.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)