Human plague--four states, 2006.

Plague is a zoonotic disease caused by the bacterium Yersinia pestis. In 2006, a total of 13 human plague cases have been reported among residents of four states: New Mexico (seven cases), Colorado (three cases), California (two cases), and Texas (one case). This is the largest number of cases reported in a single year in the United States since 1994. Dates of illness onset ranged from February 16 to August 14; two (15%) cases were fatal. The median age of patients was 43 years (range: 13-79 years); eight (62%) patients were female. Five (38%) patients had primary septicemic plague, and the remaining eight (62%) had bubonic plague. Two (15%) patients developed secondary plague pneumonia, leading to administration of antibiotic prophylaxis to their health-care providers. This report summarizes six of the 13 cases, highlighting the severity and diverse clinical presentations of plague and underscoring the need for prompt diagnosis and treatment when plague is suspected.