Animal Exposure and Human Plague, United States, 1970–2017

Stefanie B. Campbell; Christina A. Nelson; Alison F. Hinckley; Kiersten J. Kugeler


Emerging Infectious Diseases. 2019;25(12):2270-2273. 

In This Article

Abstract and Introduction


Since 1970, >50% of patients with plague in the United States had interactions with animals that might have led to infection. Among patients with pneumonic plague, nearly all had animal exposure. Improved understanding of the varied ways in which animal contact might increase risk for infection could enhance prevention messages.


Plague is a rare, life-threatening zoonosis caused by Yersinia pestis that occurs globally in discrete foci, including the western United States.[1] The bacterium is maintained in an enzootic cycle of rodents and their fleas.[2] Periodically, the cycle intensifies, leading to epizootic events characterized by localized small mammal die-offs. During epizootics, the risk for incidental human infection increases.[2] Humans are exposed to Y. pestis most commonly through flea bites but also through contact with tissues of infected animals or inhalation of infectious droplets.

Clinical manifestations of plague in humans are associated with route of exposure. Primary pneumonic plague, the most severe and rapidly fatal form of the disease, occurs after direct inhalation of infectious droplets coughed by infected animals or humans.[3] Human exposure to Y. pestis results from direct and indirect interactions with animals. Improved understanding of the role of animals in human exposure to Y. pestis may foster more refined prevention messages in plague-endemic areas.