How did people in the old days I.e. 13, 14. 15th Europe etc where able to live in filth and not die of infection, where nowdays I see everyone freaking disinfecting the shopping carriages while hacking out a lung?

by phrresehelp

I mean back then washing of hands, changing of sheets, clothes, washing dishes etc was not yet done or dine very seldom. Even if infections did happen the medicine ar their disposal was mostly willow bark, which hazel and the suction cup match thingies.