You are right, transmission from animals is really difficult. But that also explains why those transferred diseases can be so dangerous. We don't have existing immunity because humans don't hang out in bat caves. And the threat is very real when we live in close proximity to domesticated animals or eat bush meat. And people do both of those things. There is a very long list of infectious diseases that started in animals. We need to be careful. And even in richer countries the threat still exists. People keep chickens in the garden. Environmental surveys look for bats. We have factory farms and abbatoirs.