OREANDA-NEWS. A retrospective study of blood samples collected from residents of the United States in December 2019 showed that some of them had COVID-19 even before the new virus was detected in China. This is said in the article published in the journal Clinical Infectious Diseases.

Officials in China first reported of mysterious cases of pneumonia in the city Wuhan, which turned out to be caused by the new coronavirus, on December 31, 2019. In the United States, the first confirmed case of COVID-19 was reported on January 20, 2020, in a Washington State’s resident who recently arrived from China.

Researchers from the US Centers for Disease Control and Prevention analyzed over 7 thousand studied blood samples collected by the American Red Cross in nine states between December 13, 2019 and January 17, 2020. 106 samples tested positive for antibodies against coronavirus: 39 in California, and 67 in Connecticut, Iowa, Massachusetts, Michigan, Rhode Island and Wisconsin. Even taking into account possible false-positive tests, it can be stated that in the beginning of December 2019 the virus was already in the United States.