Background: On 19 January 2020, the first case of severe acute respiratory syndrome coronavirus 2 (SARS–CoV–2) infection was identified in the US, with the first cases in South Carolina (SC) confirmed on 06 March 2020. Due to initial limited testing capabilities and potential for asymptomatic transmission, it is possible that the virus was present earlier than previously thought while preexisting immunity in at–risk populations was unknown. Methods: Salivary samples from 55 SC emergency department physicians, Emergency Medical Services (EMS) providers, and medical students working as EMTs were collected from September 2019 to March 2020 as part of a separate study and stored frozen. To determine if antibody-based immunity to SARS–CoV–2 was present prior to the first recorded cases, saliva acquired post–shift was analyzed by Enzyme–Linked Immunosorbent Assay with repeat of positive or inconclusive results and follow–up testing of pre–shift samples. Results: Two participants were positive for SARS–CoV–2–reactive salivary IgG, confirmed by repeat and follow–up testing. Positive samples were from medical students working in EMS and were collected in October or November 2019. Conclusions: The presence of detectable antibodies against SARS–CoV–2 in 2019 suggests that immunity existed in SC, and the US as a whole, prior to the earliest documented cases of COVID–19. Additionally, successful analysis of banked salivary samples demonstrates the feasibility of saliva as a noninvasive tool for surveillance of emerging outbreaks. These findings suggest that emergency healthcare providers represent a high–risk population that should be the focus of infectious disease surveillance.

The authors have declared no competing interest.

This study was funded by a Transformative Seed Grant from the Health Sciences Center at Prisma Health.

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The Institutional Review Board of Prisma Health gave ethical approval for this work

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All data produced in the present study are available upon reasonable request to the authors.