They’ve known about this for years. I personally have read about the bacteria for plague being found on rodents in the Az desert as far back as 10 years ago.
Article below is it being found in California in 1984
https://www.cdc.gov/mmwr/preview/mmwrhtml/00000394.htm
There was an episode of Quincy from 1980 that dealt with Bubonic Plague on an indian reservation
http://www.imdb.com/title/tt0681878/