Arizona health officials investigating 'a sudden die-off' of prairie dogs in Townsend Winona area, which could be plague related | 13 July 2025 | After an Arizona resident succumbed to pneumonic plague in a Flagstaff emergency room, health officials are cautioning residents to be careful around sick pets and animals. Health officials are also investigating "a sudden die-off" of prairie dogs near the city [of Flagstaff], which could be plague related. The unidentified resident, who died shortly after checking into the ER with symptoms, tested positive for Yersinia pestis, the bacteria that causes pneumonic plague, the county announced Friday. The bacteria is the cause of the three most common forms of plague in humans. One of them, the bubonic plague, was known as the "Black Death" and is believed to have killed an estimated 25 million people in fourteenth-century Europe.