Perhaps I wasn't clear, but I was not visualizing insects and rodents as a host animal. I was visualizing urban vermin tracking assorted bodily fluids from one slum apartment to the next. I have (for family reasons) been in the projects several times, and I am used to the smell of all sorts of things that should have gone down the drain but didn't, both from behind closed doors and from the still soggy carpets and the damp yet sticky stairs. Throw in the critters that crawl around, and a deadly virus, and I expect transmission to occur. I don't think it will explode by a factor of 50,000,000 in a year like the Flu does, but I think it could realistically be hard to get rid of.
You have a point there.
Not everyone in the ‘hood buys into the germ theory of disease transmission and we keep importing people who share those doubts. Just wander through your local barrio and ask for a witch doctor.
Why spend energy on biohazard cleanup when you can nail a rooster leg the door.