The plague has killed a second person in Colorado this year.
Pueblo County announced Wednesday that an adult there had died of the disease, which was likely spread by fleas from a dead animal.
Cases of the plague are rare, and deaths are even rarer. Nationally, an average of seven human plague cases is reported each year, although Colorado had eight on its own last year.
In June, a 16-year-old from Larimer County died of septicemic plague that wasn't detected until after he passed away. That's a relatively rare form of the flu that is difficult to diagnose because it isn't accompanied by the tell-tale swelling of the glands seen in most plague cases.
The latest case is also believed to have been the same type.