Does plague occur naturally in the United States and in Arizona?
Yes. Today, plague remains a naturally occurring infection of rats, ground squirrels, prairie dogs, and other rodents on every populated continent except Australia. In the U.S. plague is most common in the southwestern states, particularly New Mexico and Arizona. An average of 1 to 2 cases of human plague occur naturally each year in Arizona. Most cases are seen in the northwest portion of the state, although cases can likely occur anywhere in the state above 4000 feet of elevation.
