The highly infectious coronavirus variant first detected in the U.K. is now the dominant version in the U.S., Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said Wednesday. The announcement stoked fears of a looming fourth wave of the coronavirus pandemic in the United States. Public officials warned in January that the B.1.1.7 variant that surged in Britain late last year could become the dominant source of new infections in the U.S. The number of new deaths in the U.S. has continued to decline since a winter surge as more people are vaccinated, including elderly people and other vulnerable populations. But Walensky said on Wednesday that 52 of the CDC's 65 jurisdictions are reporting cases of new "variants of concern."

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