[cheerfulgreek]

Originally Posted by LAblondeGPhi

I always thought that natural selection and population resistance had something to do with it, in addition to basic hygiene and city planning. Several major rounds of plague destroyed pretty large portions of the population in some cases. In the middle ages, a major bout wiped out more than a third of the European population. Isn't that classic Darwinism?

Also, it's a bacterial infection, so several antibiotics are effective treatment against it, no?

Well, I don't know much about the history of diseases/viruses as far as how many civilizations were wiped out because of it. However, I do know that under some circumstances, diseases change little in their virulence or even get worse. Moreover, some, like bubonic plague, appear to oscillate in virulence.

Yep. It's caused by the bacterium Yersinia pestis, which infects many animals, especially rodents. From these it can be transmitted to humans (and their cats and dogs) by fleas.