the plague is endemic to eastern colorado ... prairie dog colonies host the plague-carrying fleas ... the most common trans-species infections occur when fools let their dogs run through the colonies and bring home the plague-carrying fleas ... we typically get a few cases of plague here every summer ...
It's not a real big deal if you treat it early enough.
Seems the Plague came into the US from China around 1900 in San Francisco but was covered up and never publicized.
Given how disgusting and unsanitary our rat infested our cities are becoming and how "homeless" drug addled people live in very close proximity to these rats it would not take much to start another mini pandemic and San Francisco or LA would be the perfect place for it to start.