There have been several waves of mortality due to infections of Yersinia pestis, the most famous wave being the Black Death. Most of us think of this as a Medieval disease but plague persists and even smolders in the US. In the American southwest, plague is of conservation concern since it can obliterate prairie dogs and their predator, the endangered Black-footed Ferret.
Transmission to humans is rare but happens and I remember seeing warnings of plague on a reality survival show. Fleas are the primary vector and jump from host to human and spread plague.
I remember reading about a human-dog case of plague here from last year. Now there's a case of plague in a cat from Colorado.