From Ice Age Farmer Wiki
Plague was mentioned in IAF Podcast Episode 10. Kathy A wrote in in episode episode 11 to let us know that one can actually keep track of the trends of Plague cases via the CDC's web site.
Jason S. adds also that Bubonic Plague is bacteria, so antibiotics or even colloidal/ionic silver may assuage most concerns here.
- See also: Thieves Oil