The novel coronavirus may have infected people in the United States as early as Dec. 13, 2019, according to a study published Monday in the journal Clinical Infectious Diseases.
The study, which was conducted by scientists at the US Centers for Disease Control and Prevention, analyzed blood donations collected by the American Red Cross from Dec. 13, 2019 through Jan. 17, 2020.
The 7,389 samples, collected from nine states, were tested for SARS-CoV-2 reactive antibodies. SARS-CoV-2 is the scientific name for the coronavirus that causes Covid-19.
Of the samples tested, at least 106 were found to have antibodies for SARS-CoV-2, including ones collected from California, Oregon and Washington from Dec. 13 through Dec. 16, 2019.
“SARS-CoV-2 infections may have been present in the U.S. in December 2019, earlier than previously recognized,” the authors wrote.
Previously, the first known case of Covid-19 in the US was reported on Jan. 21.
CNN has reached out to the World Health Organization for comment.