Respiratory Tract Samples Collected from Patients in a Region of Quebec, Canada, Indicate the Absence of Early Circulation of SARS-CoV-2 Infection

Background: The first documented case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in Quebec was confirmed on February 27, 2020. Retracing the first cases that occur within a geographical region may provide insight regarding the evolution and spread of SARS-CoV-2 in that region because the spread of undiagnosed cases may facilitate the initial community amplification of the virus.

Methods: We performed a retrospective analysis of respiratory tract samples collected for influenza testing in a region of Quebec, Canada, to look for evidence of early circulation of SARS-CoV-2. Frozen nucleic acid extracts initially collected for influenza testing between January 1 and February 20, 2020, were tested for SARS-CoV-2 using a reverse transcription-polymerase chain reaction assay.

Results: During the study period, 1,440 of 2,121 (67.9%) nucleic acid extracts from individual patients were available for retrospective testing. None of the samples tested positive for SARS-CoV-2.

Conclusions: The results suggest that SARS-CoV-2 was not circulating within the region before February 20, 2020, because many samples, representing more than two-thirds of all samples tested for influenza during early 2020, were tested. Further studies using a similar methodology to determine the date of onset of SARS-CoV-2 in different countries and geographic areas could enhance our understanding of the current pandemic.