Charles wrote:

Bubonic plague is carried by rodents in the southwestern United States and there are a few cases each year.

Brings back memories. Around 1982 I did a tour of the various Native American ruins in the SW. At Chaco Canyon, there were signs in the campground informing visitors that fleas were present that might be infected with plague. I slept that night sealed in my car rather than unpack my camping gear and get closer to nature.