Health experts say having a vaccine is just one front in a two-front battle against Covid-19. The other is effective treatments for those who are already sick with the disease. WSJ breaks down the three most promising types in development. Photo Illustration: Jacob Reynolds/WSJ
By
Updated Dec. 1, 2020 11:20 am ET

The new coronavirus infected people in the U.S. in mid-December 2019, a few weeks before it was officially identified in China and about a month earlier than public health authorities found the first U.S. case, according to a government study published Monday.

The findings significantly strengthen evidence suggesting the virus was spreading around the world well before public health authorities and researchers became aware, upending initial thinking about how early and quickly it emerged.

Scientists at the U.S. Centers for Disease Control and Prevention found evidence of infection in 106 of 7,389 blood donations collected by the American Red Cross from residents in nine states across the U.S., according to the study published online in the journal Clinical Infectious Diseases.