When I think about how plagues came about, the biggest aspect I can think of is that humanity just spread. From the emergence of cities, to the silk route between Asia and Europe. When cities first started to emerge there was obviously no running water or sewage system to keep things from being contaminated. We went over this in class, but this has also been talked about in almost every history course you can take. The spread of disease was extremely easy back then because animal waste, human waste, etc. was just on the sides of the streets.

Another big cause of the spread of disease was that humans hundreds of years ago had no understanding of what bacteria was. It wasn’t until Ignaz Semmelweis decided to wash his hands before going to deliver a baby that there was any understanding that maybe there is something on our hands that is in fact causing childbed fever.