Fatal Plague in the US


By Carol A. Kemper, MD, FACP, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center. Dr. Kemper reports no financial relationship relevant to this field of study.
This article originally appeared in the November 2006 issue of Infectious Disease Alert. It was edited by Stan Deresinski, MD, FACP, and peer reviewed by Connie Price, MD.

Source: CDC. MMWR Morb Mortal Wkly Rep. 2006;55:940.

Each year in the United States, a few isolated cases of plague are reported. This year, possibly because of increased spring rains leading to an increase in the rodent population, an unprecedented 13 cases of plagues have occurred in 4 states (New Mexico, California, Colorado, and Texas). Importantly, 5 (38%) patients had primary septicemic plague and, therefore, lacked an obvious tell-tale buboe. The remaining 8 (62%) patients had bubonic plague, 2 of whom developed secondary pneumonia. Two patients (15%) died.

Most human infection is acquired through the handling of infected animals (eg, domestic cats, rabbit and hare carcasses, squirrels, chipmunks) and from the infected fleas of various rodents. Pneumonic plague is highly contagious, and any individual with suspected disease should be placed in respiratory isolation. Family members, close contacts, and exposed health care workers require post-exposure prophylaxis with doxycycline. Delays in recognition of infection lead to an increased risk of mortality, as occurred in this report. Septicemic and pneumonia plague is quickly fatal if not promptly treated, and bubonic plague is about 50% fatal if not recognized.

Possible sources of infection in the current MMWR report included rabbit carcasses from Lea County, New Mexico and from Kern County in northern California, and infected fleas from various rodents on the victims' properties. Dogs owned by 3 of the victims had serologic evidence of past infection with Y. pestis. In one case, a 28-year-old woman living in Los Angeles came in contact with the raw meat from the Kern County bunny, presumably brought home for cooking. She developed painful right axillary swelling, fever, and septic shock. Because she had not traveled outside of Los Angeles and had none of the usual risk factors for plague, plague was not suspected.

As an aside, human plague in the developing world is much more common than in the United States. An outbreak of suspected pneumonic plague in the Congo this year has resulted in more than 100 deaths, promulgated by working conditions in crowded and poorly ventilated mines, leading to increased human transmission.