I don't know if you remember the very first years of AIDS. I do. Method of transmission of it WAS NOT KNOWN.
An 82-year old nun came down with it, as did hemophiliacs, homosexuals, heroin addicts and Haitians. I remember the "four h's" and they weren't the 4-H club!
But WHO could figure it out from THOSE statistics? It was very, very SCARY!! NOW we know: exchange of body fluids.
This is similar. Right out of Africa.
ASIA produced leprosy and the Bubonic plague, diseases of filth.
Aren't we lucky to have been born in the West?
I must rise and speak in defense of leprosy, or at least what we now refer to as leprosy (aka Hansen's disease.) It's not a disease of filth. It requires long term close exposure AND losing the genetic lottery (by being one of the about 3% genetically susceptible) to acquire it, NOT poor hygene. I speak as one who has diagnosed, treated and cured leprosy. Not to detract from your general point, but don't tar the lepers with this.