The more transmisible B.1.1.7. coronavirus variant, which first emerged in the U.K., currently accounts for about 26 percent of cases in the U.S., according to Rochelle Walensky, MD, CDC director.
The estimate is based on the CDC's most recent data, Dr. Walensky said during a March 31 news conference, adding that it's on its way to becoming the dominant strain in many areas of the country.
"We are looking at it by region," she said. "It varies in region from 4 to 35 percent, and so we're watching this very carefully. But it is starting to become the predominant variant in many U.S. regions."
The U.K. variant is already the predominant strain in at least five regions of the country, Dr. Walensky said.
"We do know it's more transmissible — somewhere between 50 and 70 percent more transmissible than the wild-type strain. So to the extent that people are not practicing those standard mitigation strategies, we do think that more infections will result because of B.1.1.7."
As of March 30, there were 11,569 reported cases of the variant, according to CDC data. Florida had the highest number at 2,351, followed by Michigan, where 1,327 cases have been reported.