Pneumonic plague, a severe lung infection, is rare in humans, with only about seven cases reported annually in the US. The death of the Coconino county resident marks the first recorded pneumonic plague death in the county in 18 years but not the most recent human plague case in Arizona – the state has recorded seven cases of plague since 2006. County officials have said they do not think the human plague death and the prairie dog mortalities are related. Coconino county health officials said the risk of human-to-human transmission of pneumonic plague is low. But the timing of the human plague death, and the prairie dog die-off, is raising concerns.