> Second of all, RaTG13 has never been isolated. It exists as fragments of RNA in a fecal swab. Its genome has been reconstructed from sequences of RNA samples, but actually extracting a replicating virus from a fecal swab is a major undertaking.
The lab in question was sent tissue samples extracted from the miners who died of RaTG13. These presumably would have live virus on them.
WIV received serum samples, not tissue. Nobody knows what the miners died of, because several different viruses have been discovered in the same cave, and the miners' samples tested negative for SARS-related coronaviruses. If they had RaTG13 or SARS-CoV-2, it didn't show up in antibody or PCR tests.[1]
However, the miners' story shows you why virologists consider natural zoonosis overwhelmingly likely. Miners, people who raise livestock, butchers, and millions of other people throughout China are in close contact with possibly infected animals every day. Spillover events are probably not uncommon: it's estimated that most (about 95%, in the countryside) spillover events of SARS-CoV-2-like viruses do not cause sustained outbreaks.[2] A few people get sick, and then the virus dead-ends. The virus' best chance is if someone who's infected travels to a major population center, where the virus has a higher chance of spreading. The virus' chance of survival is estimated to increase to about 30%, in that case.
The lab in question was sent tissue samples extracted from the miners who died of RaTG13. These presumably would have live virus on them.