First US COVID cases may date back to mid-December 2019

A new National Institutes of Health (NIH) analysis of more than 24,000 stored blood samples reveals SARS-CoV-2 antibodies in nine participants in five states as early as Jan 7, 2020, indicating that COVID-19 was in the country weeks before the Centers for Disease Control and Prevention (CDC) announced the first US case on Jan 21. Because immunoglobulin G (IgG) antibodies aren't detected until about 2 weeks after infection, the findings date the exposures to late December, although whether the participants were infected in the United States or abroad is unknown.