[achenatx]

You cant really tell from the genetics. You can chop and insert any arbitrary sequence into RNA/DNA.

Instead what they do is look at the animal population in the region for highly related or identical versions. If it was natural transmission you would expect animals to be infected with a strain that is extremely similar to the virulent strain.

What this is saying is that there has been no discovery of an intermediate host which has a highly related genome. This would happen if the version that spread in humans had been incubated in a lab for a long time and had undergone enough mutations in the lab to be very dissimilar to natural versions.

<<Investigators now face the reverse situation for tracing the origins of SARS-CoV-2: a paucity of evidence and a cold trail. Closely related bat SARSr-CoVs have been identified, but there is still no sign of an intermediate host 1.5 years into the pandemic. The closest bat virus relatives have been found in Yunnan province about a thousand miles away from Wuhan in Hubei province [17–19]. >>