Thank you for this very interesting and necessary discussion about the origin of SARS-CoV-2.
I think that an alternative scenario to explain the presence of ancestral viral lineage A in other wildlife markets (OWLM) and of lineage B in the Huanan seafood and wildlife market (HSWLM) is that the outbreak in the HSWLM was initiated by an infected human and not by an infected animal. In this scenario, a wild animal infected with lineage A was transported to a OWLM where the first spillover to humans occurred. Then, intra-host evolution from lineage A to lineage B may have occurred in an individual that probably work at or that frequently visited different wildlife markets and this individual initiate the secondary SARS-CoV-2 lineage B outbreak in the HSWLM. This scenario may explain why none of the animals sold at the HSWLM tested positive for SARS-CoV-2, because transmission was initiated by humans that mainly circulated where wildlife or wildlife products are sold.
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