A new antibody testing study examining samples originally collected through the National Institutes of Health’s All of Us Research Program found evidence of SARS-CoV-2 infections in five states earlier than had initially been reported. These findings were published in the journal Clinical Infectious Diseases. The results expand on findings from a Center for Disease Control and Prevention Study that suggested SARS-CoV-2, the virus that causes COVID-19, was present in the U.S. as far back as December 2019
In the All of Us study, researchers analyzed more than 24,000 stored blood samples contributed by program participants across all 50 states between Jan. 2 and March 18, 2020. Researchers detected antibodies against SARS-CoV-2 using two different serology tests in nine participants’ samples. These participants were from outside the major urban hotspots of Seattle and New York City, believed to be key points of entry of the virus in the U.S. The positive samples came as early as Jan. 7 from participants in Illinois, Massachusetts, Mississippi, Pennsylvania, and Wisconsin. Most positive samples were collected prior to the first reported cases in those states, demonstrating the importance of expanding testing as quickly as possible in an epidemic setting.
In the United States, the first COVID-19 infection was reported on 19 January 2020 in a returned traveler from China, 2 days after domestic testing was initiated. While the first confirmed case had a symptom-onset date of 19 January 2020, 2 others within the first 12 US cases identified had illness-onset dates of 14 January 2020. Some reports have suggested the introduction of SARS-CoV-2 into the United States may have occurred earlier than initially recognized, although widespread community transmission was not likely until late February.
Early phylogenetic analyses suggest that SARS-CoV-2 may have evolved between October and December 2019. While the first recorded COVID-19 case outside of China was identified in Thailand on 13 January 2020, retrospective NAT identified a respiratory specimen with molecular evidence of SARS-CoV-2 from a patient hospitalized in France on 27 December 2019. Similarly, in the United States, retrospective NAT of archived respiratory samples in the Seattle region have suggested the introduction of SARS- CoV-2 virus into the Seattle, Washington, area between 18 January and 9 February 2020
Antibodies are proteins produced in the blood in response to an infection, such as a virus. They play a critical role in fighting infections and are helpful signs that a person may have been exposed to an infection in the past, even if they didn’t show symptoms. In the All of Us study, researchers looked in participant samples for a type of antibodies called IgG. These antibodies do not appear until about two weeks after a person has been infected, indicating that participants with these antibodies were exposed to the virus at least several weeks before their sample was taken. In this study, the first positive samples came from participants in Illinois and Massachusetts on Jan. 7 and 8, 2020, respectively, suggesting that the virus was present in those states in late December.
The study reveals that these findings indicate that SARS-CoV-2–reactive antibodies were detected in 106 specimens, a small percentage of blood donations from California, Oregon, and Washington, as early as 13–16 December 2019. The presence of these serum anti-bodies indicate that isolated SARS-CoV-2 infections may have occurred in the western portion of the United States earlier than previously recognized or that a small portion of the population may have pre-existing antibodies that bind the SARS-CoV-2 S protei