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


More than 50% of patients in the United States with plague since 1970 had animal interaction that might have directly or indirectly led to their exposure to Y. pestis. Animals are associated with human plague transmission in varied ways, ranging from direct exposure, such as caring for a plague-infected animal, to more subtle indirect encounters with infected fleas, such as by co-sleeping with a flea-infested pet in an area with epizootic plague. Nearly all patients with pneumonic plague had animal interaction before illness, and several occurred in an occupational setting. Although the frequency of human plague in the United States has decreased, the proportion of human cases potentially related to animal exposure has concomitantly increased.

Cat-associated and wild animal–associated human plague have been documented in previous reports.[6–9] More recently, the severity of plague illness in dogs and the role these animals might play in human plague have been recognized.[10] A cluster of pneumonic plague in Colorado was linked to a dog with pneumonic plague,[11] and a recent case of canine plague resulted in the potential exposure of ≥116 persons at a veterinary clinic.[12] Gould et al. found that co-sleeping with a dog occurred more frequently among human plague case-patients than among neighborhood controls.[13]

Limitations of our analysis include the possibility that human plague cases might have gone undiagnosed and thus were not captured. Our findings might underrepresent animal-associated plague because case records contain variable levels of detail. Thus, some patients might have had animal exposures that were not captured. In many instances, we could not determine which exposure contributed to human illness, if any at all. Therefore, this analysis is meant to describe the potential rather than definitive scope of animal-related human plague.

This report offers perspective on frequency and diversity of animal interaction as possible means of human exposure to Y. pestis in the United States. Given that most human plague worldwide is caused by flea bites, animal-associated prevention messages have been geared toward hunters and trappers, including the use of gloves when handling or skinning wild animals. Our findings highlight One Health–oriented opportunities to maximize plague prevention through communication with veterinarians in plague-endemic areas. Veterinarians play an integral role in plague prevention for animals and humans by increasing use of flea prevention products, promoting basic precautions among pet owners caring for sick pets, and encouraging use of appropriate personal protective equipment in the veterinary community.