they've been having plague in these rodents for YEARS FFS.
South Dakota,Oregon, Colorado, Wyoming, I could go on.
https://www.cbsnews.com/news/oregon-man-diagnosed-with-black-death-plague/
https://www.nydailynews.com/life-style/health/bubonic-plague-survivor-speaks-recovery-article-1.1600598
https://slate.com/technology/2015/10/plague-kills-americans-and-spreads-in-yosemite-national-park.html
2015 has been a busy year in the United States for human cases of plague—the very same disease that caused the Black Death in the 14th century, sporadic outbreaks across Europe for hundreds of years after that, and epidemics numbering into the hundreds of thousands of cases in India and into the millions of cases in China in the 20th century. To date, 15 cases have been diagnosed this year in the United States, three of them fatal. Several of the cases have been linked to visits to Yosemite National Park.
Plague has been in the United States for around as long as the Ford Motor Company or the Nobel prizes have existed. The bacterium likely arrived on a steamer from our newly annexed territory of Hawaii, which was experiencing its own plague epidemic