When did the coronavirus start spreading in the U.S.? Likely in January, CDC analysis suggests
How early did local transmission of the SARS-CoV-2 virus begin in the United States? For the second time this week, scientists have proposed a new estimate. This one, from scientists at the Centers for Disease Control and Prevention, suggests transmission likely began in late January or early February and that the virus spread undetected for more than a month.
The findings, published Friday in the CDC’s online journal Morbidity and Mortality Weekly Review, challenge to a degree those released earlier this week in a pre-print article from Michael Worobey, a professor of evolutionary biology at the University of Arizona. Pre-print articles have not yet undergone the normal peer-review process at a scientific journal.
