User blog comment:EiplecOco/Bubonic plus Pneumonic/@comment-32656-20140331152221/@comment-4621372-20140331203401

Poor, starved people? Sounds like Europe around that time!

But, yeah. Most diseases have little effect because there needs to be a perfect balance between lethality and infectivity. Ebola, for instance, is extremely deadly, but is not very contagious, so it burns out fast. Flu, on the other hand, is extremely contagious- but not very deadly.

By the way, you forgot one plague- the most dangerous; Septicemic.