Sars-Cov-2

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.

The coronavirus was present in the U.S. weeks earlier than scientists and public health officials previously thought, and before cases in China were publicly identified, according to a new government study published Monday.

The virus and the illness that it causes, COVID-19, were first identified in Wuhan, China, in December 2019, but it wasn't until about Jan. 20 that the first confirmed COVID-19 case, from a traveler returning from China, was found in the U.S.