[@Antarctic Termite]

Provided these environments haven't given rise to an evolved state of bacteria that forms as much a symbiotic relationship with them as the house, therefore creating something that would impress even Code Talker.

The other probability is they have a built up immunity. Both man and person would be eating out of trash anyways, let alone sleeping and interacting with it. They breath the no-doubt spore-clogged air. If they're not going to die early, they at least maybe got a battled-hardened immune system that'll probably strangle both of them if it ever hiccups and mutates in on itself.

But in reality, a person like that - pets included - need help irregardless and the place needs to be burned down. Not cleaned up or demolished. Just burned down. It'll do more sterilization to it than any application of anti-fungicide and disinfectant.