Researchers, including scientists from the Centers for Disease Control and Prevention (CDC) and the American Red Cross, have found evidence that Covid-19 was present in the U.S. in December 2019, weeks earlier than previously thought and before even the first cases in Wuhan, China, had been publicly identified.

https://www.forbes.com/sites/roberthart/2020/12/01/study-suggests-covid-19-was-in-the-us-weeks-earlier-than-thought-before-first-public-cases-in-china/?sh=5354f2d54bf8

Researchers found positive test results, indicating prior exposure to the virus responsible for Covid-19, in samples from California, Oregon and Washington in mid-December, much earlier than the first official U.S. case on Jan. 19.

Samples from Connecticut, Iowa, Massachusetts, Michigan, Rhode Island, and Wisconsin were also found to test positive for Covid-19 in January, before Covid-19 was believed to be present.

Findings from the study, which tested stored blood samples from between December 2019 and January 2020 for Covid-19 antibodies and were published in the journal Clinical Infectious Diseases, indicated the presence of Covid-19 in several U.S. states “earlier than previously recognized.”