Connecting clusters of COVID-19: an epidemiological and serological investigation.

Background: Elucidation of the chain of disease transmission and identification of the source of coronavirus disease 2019 (COVID-19) infections are crucial for effective disease containment. We describe an epidemiological investigation that, with use of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serological assays, established links between three clusters of COVID-19.

Methods: In Singapore, active case-finding and contact tracing were undertaken for all COVID-19 cases.