To determine when severe acute respiratory syndrome coronavirus 2 arrived in Congo, we retrospectively antibody tested 937 blood samples collected during September 2019-February 2020. Seropositivity significantly increased from 1% in December 2019 to 5.3% in February 2020, before the first officially reported case in March 2020, suggesting unexpected early virus circulation.
Keywords: 2019 novel coronavirus disease; COVID-19; Central Africa; Luminex; Republic of Congo; SARS-CoV-2; coronavirus disease; microsphere immunoassay; respiratory infections; retrospective study; serology; severe acute respiratory syndrome coronavirus 2; viruses; zoonoses.