And to clarify, it's not just that they disbelieved that sickness was caused by little tiny nasties too small for the eye to see. It's that they literally insisted that it was nonsense that cleanliness and infection had anything to do with one another at all, and wouldn't so much as bother to wash their hands prior to surgery. This is as recent as the american civil war.

The concept of dirt and filth causing infection simply was not known prior to the 19th century. It just wasn't. That is documented fact. Sorry to burst the bubble.