Covid Omicron Variant BA.2.12.1 Spreading Quickly Across United States; Related Cases Up Nearly 100% In Past Two Weeks

covid omicron ba.2.12.1
Covid molecule NIAID

In February, the first few cases of two new, more infectious variants were identified in the Northeastern United States. Dubbed BA.2.12.1 and BA.2.12.2, these sublineages of the BA.2 variant made up only 1.5% of newly-sequenced positive tests before March 19.

But, warned New York State Public Health officials, the new variants are thought to have a 23%–27% growth advantage over BA.2, which itself had an estimated 30% growth advantage over the original Omicron. About 6 weeks later, the numbers support that theory.

For the week ending April 16, BA.2.12.1, which seems to be the more dominant of the two, made up 19% of all newly-sequenced positive Covid tests in the country. Centers For Disease Control data released today show that BA.2.12.1, now makes up 36.5% of all newly-sequenced positive Covid tests. That’s a jump of close to 100% in the past two weeks.

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The share of cases related to BA.2.12.1 is even higher in some parts of the U.S.

In the Northeast region defined by New York, New Jersey and Connecticut, where the variant first took hold, it now accounts for 61% of all new cases. Nearby, in the region made up of Delaware, D.C., Maryland, Pennsylvania, Virginia and West Virginia, the share is 40%.

In the Southwest, which seems to be about 2-3 weeks behind the Northeast in the spread of many recent variants, numbers are much lower. CDC figures indicate that in California, Nevada and Arizona, BA.2.12.1 now accounts for 20% of new cases. Across Arkansas, Louisiana, New Mexico, Oklahoma and Texas it is 13.9%. The region defined by Alaska, Oregon, Washington and Idaho has identified the variant in only 12% of its most recent cases.

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The share of BA.2.12.1 regionally the U.S. (in red) vs. BA.2 (in pink). CDC

See the map to the left for a graphical representation of the share of BA.2.12.1 vs. BA.2, which became dominant across the country only four weeks ago.

And the freight train hasn’t stopped with BA.2.12.1. Just last week, the first cases of two even newer variants, also thought to be more infectious than BA.2, were discovered in the U.S.

As the variants have spread, cases and hospitalizations have begun to rise, as well. The 7-day average number of cases in the country has risen from about 25,000 in late March to more than 56,000 today, a 100+% rise. The 7-day average number of patients hospitalized with Covid in the U.S., which generally trails a rise in cases by about two weeks, has risen from a recent low of about 25,000 on April 4 to over 56,000 cases in late April, also a more than 100% rise, despite the standard lag of two weeks between a rise in cases and hospitalizations.

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