Omicron Now Accounts for 95% of U.S. Covid Cases, CDC Says

(Bloomberg) -- The omicron variant is accounting for the lion's share of new coronavirus cases as Americans return to work and school following the holiday season, according to estimates from federal health officials.

Omicron made up 95% of all sequenced Covid-19 cases in the U.S. in the week ending Jan. 1, up from a revised 77% in the previous week, according to a model by the Centers for Disease Control and Prevention. Previously, the CDC estimated that the variant accounted for 58.6% of cases in the week ending Dec. 25. 

The CDC's Nowcast estimates levels of variant prevalence based on genomic-sequencing data. It can be volatile, with substantial revisions to weekly numbers as the agency gathers more samples from across the country.

With omicron tightening its grip across the country -- it is now the prevailing strain in every geographic region tracked by the model -- the once-dominant delta variant, which spurred a nationwide jump in cases last year, now accounts for just 4.6% of sequenced cases, according to the CDC.

Omicron was first identified in South Africa and classified by the World Health Organization as a variant of concern in November. It has swept through the U.S. since being detected in California on Dec. 1. 

Health officials have been working hard to monitor its spread and are encouraging all adults to get booster doses. Late last year, President Joe Biden called on care providers to expand the availability of Covid vaccines and boosters in a bid to hold off omicron and combat a winter surge of infections.

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