Comment by Blanca E. Ruiz-Medina

The Wuhan wet markets where wild animals are sold represent a strong scenario for zoonotic transfer. However, isolation of SARS-CoV-2 or its immediate predecessor from wild animals in their natural environment has yet to be documented. Due to incomplete evidence for a zoonotic origin, a laboratory origin is plausible. [...] Overall, there is stronger evidence supporting a zoonotic transfer. However, lack of transparency has given way to maintain the laboratory leak hypothesis alive. Because of the implications, the two scenarios should remain on the table, and additional vigorous investigations are needed to reach a conclusion about the origin of SARS-CoV-2.