U.S. government figures show that the omicron variant continues to account for a growing proportion of new coronavirus infections in the country.

Omicron accounted for 59% of new cases in the U.S. for the week ending Dec. 25, according to updated data from the Centers for Disease Control and Prevention. That’s up from 23% the previous week.

The CDC had said last week that omicron already accounted for a majority of new cases in the country. But the agency said Tuesday it significantly lowered that previous estimate based on additional data it collected.

Still, it noted that omicron is accounting for a growing proportion of cases.

The rapid spread comes after the first confirmed case of omicron in the U.S. was identified earlier this month. Studies have provided early hints that it is milder than the delta variant.