The Omicron variant was estimated to be 58.6% of the coronavirus variants circulating in the United States for the week ending Dec. 25, according to data from the US Centers for Disease Control and Prevention (CDC).

The fast-spreading variant was first detected in southern Africa and Hong Kong in November, with the first known case in the United States identified on Dec. 1 in a fully vaccinated person who had traveled to South Africa.

The Delta variant accounts for 41.1% of all US COVID-19 cases, according to the public health agency's data on Tuesday.

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The agency said the data includes modeled projection that may differ from weighted estimates generated at later dates.