A more easily spread coronavirus variant first identified in England last year has now become the dominant strain in the U.S., the head of the Centers for Disease Control and Prevention said Wednesday. The variant, known as B.1.1.7, spread quickly across the United Kingdom and Ireland beginning last fall, with the more infectious version of the coronavirus thwarting restrictions and lockdowns that had earlier helped keep the original strain in check. B.1.1.7 is "now the most common lineage circulating in the United States," CDC Director Rochelle Walensky said at a White House media briefing on Wednesday. The announcement comes as the number of cases — particularly among younger Americans — has been on the rise in the U.S., fueling fears that the nation may be facing yet another deadly surge. Walensky said that the newer strain has been shown to be more transmissible among younger people and that new outbreaks in the U.S. have been linked to youth sports and day care centers.