Most of the decline of infectious diseases has come about not through medicine, but through plumbing; by isolating the contents of the human large intestine from contact with human skin, upper gastro-intestinal tract and lungs.
So when people insist on messing about with those contents, we shouldn’t be surprised if they get sick.
I have a personal theory that an SF bathhouse scene with massive numbers of people never developed earlier in history because in a pre-antibiotics world they would have all just died in short order. Self-limiting, in other words.
Geesh, that’s stark. True, but stark. When I think of what the boys do to each other, I’m reminded of Jim Carey’s great line: “What possesses a guy to look over at a beautiful woman lying in bed next to him and say, ‘You know, I could really stand to see a little more hair on that ass.” Beats me!