Incidence in the United States

• Since 1900, plague has been endemic in the U.S.
• Between 1970 and 2003, 2% of plague has been pneumonic, 83% has been bubonic and 15% has been septicemic.
• Approximately 5 to 15 cases occur each year in the U.S. The greatest concentration occurs in Arizona, Colorado, and New Mexico. But human cases have occurred in rural areas from the Pacific coastal region eastward to the Great Plains states.
• Between 1970 and 2003, case numbers have ranged between 1 and 40 cases each year in the U.S. Peak occurrence is between April and November.
• The last time person-to-person transmission occurred in the U.S. was during the epidemic of 1924-1925 in Los Angeles, California.