Yosemite National Park, California - Someone found with and being treated for the Plague, which follows two deaths earlier in the year.
Apparently:
The Centers for Disease Control and Prevention reports that the United States has about seven annual cases, over 80% of which have been in the bubonic form.
Thus, the four human cases reported so far in 2015 appears to be in line with those numbers.
Until now, California hadn't had an instance of human plague since 2006, when there were three cases in Mono, Los Angeles and Kern counties, according to state health officer Dr. Karen Smith. There have been 42 cases in the state since 1970, of which nine proved fatal.
"Although this is a rare disease, people should protect themselves from infection by avoiding any contact with wild rodents," Smith said.