WASHINGTON (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 per cent of all sequenced Covid-19 cases in the United States in the week ending Jan 1, up from a revised 77 per cent in the previous week, according to a model by the Centres for Disease Control and Prevention (CDC).
Previously, the CDC estimated that the variant accounted for 58.6 per cent 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 per cent of sequenced cases, according to the CDC.
Omicron was first identified in South Africa and classified by the World Health Organisation as a variant of concern in November. It has swept through the US 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-19 vaccines and boosters in a bid to hold off Omicron and combat a winter surge of infections.