The first case of SARS-Cov-2 in the United States was reported on January 19, 2020 in Washington State, but phylogenic data and retrospective nucleic acid testing of archived samples suggest it may have been earlier. To this end, researchers at the U.S. Centers for Disease Control and Prevention and the American Red Cross screened archived samples from blood donors collected from December 13, 2019 to January 17, 2020 from nine states. Samples were screened using an enzyme linked immunosorbent assay (ELISA) against the spike-1 and spike-2 proteins of the SARS-CoV-2 virus, microneutralization tests with live SARS-CoV-2 virus, the Ortho pan Ig ELISA specific for SARS-CoV-2, and an assay to measure the ability of sera to block the interaction between the viral S receptor and the ACE2 cellular receptor. Of the 7,389 samples screened, 106 (1.4%) were confirmed positive based on signal to threshold ratios >1 for the ELISA against the spike-1 and -2 proteins.samples collected from December 13-16, 2019 in California, Oregon and Washington were positive along with and 67 samples collected from December 30, 2019 and January 17, 2020 in Massachusetts, Wisconsin, Iowa, Michigan, Connecticut, and Rhode Island. Although cross-reactivity to common coronaviruses was considered, further testing of these and other blood donation samples may help confirm that SARS-CoV-2 was introduced earlier in the United States than previously thought.
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