GlobalHealth Threats

A study published in Clinical Infectious Diseases has found evidence of antibodies to COVID-19 as early as December 2019. The first confirmed COVID-19 case was reported on 21 January in Washington State, in a traveller recently returned from China.

Archived blood samples from the American Red Cross were investigated for antibodies to SARS-CoV-2, the virus responsible for COVID-19. Over 7,300 residual samples collected across nine states between 13 December 2019 and 17 January 2020 were analysed. Of these 106 (1.4%) samples showed reactivity to SARS-CoV-2. This included 39 samples collected between 13-16 December in California and Oregon or Washington. The remaining positive samples were collected between 30 December 2019 to 17 January 2020, from residents in Connecticut or Rhode Island, Massachusetts, Michigan and Wisconsin or Iowa.

Upon further testing, the researchers ruled out cross-reactivity to other coronaviruses in 84 of 90 tested samples.

Since reactive antibodies were found in several western states before the first diagnosed case in the US, and across another six states before the first known introduction into those states, the authors conclude that their “findings suggest that SARS-CoV-2 may have been introduced into the United States prior to January 19, 2020.” They also caution that it is unknown whether the virus was circulating in the United States, or they were travel associated.