Doesn't even need the mutation. It may be that it is infectious with R0>1 to some other animals as is, but with few health effects so we don't notice it. If so

Doesn't even need the mutation. It may be that it is infectious with R0>1 to some other animals as is, but with few health effects so we don't notice it. If so, it'll just immediately get reintroduced to humans even if we distance it out of our population successfully. No mutations required.