Interannual Variability of Human Plague Occurrence in the Western United States Explained by Tropical and North Pacific Ocean Climate Variability

Tamara Ben Ari Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway; Ecole Normale Superieure, Paris, France; Climate Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California; Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado

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Alexander Gershunov Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway; Ecole Normale Superieure, Paris, France; Climate Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California; Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado

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Rouyer Tristan Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway; Ecole Normale Superieure, Paris, France; Climate Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California; Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado

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Bernard Cazelles Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway; Ecole Normale Superieure, Paris, France; Climate Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California; Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado

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Kenneth Gage Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway; Ecole Normale Superieure, Paris, France; Climate Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California; Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado

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Nils C. Stenseth Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway; Ecole Normale Superieure, Paris, France; Climate Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California; Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado

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Plague is a vector-borne, highly virulent zoonotic disease caused by the bacterium Yersinia pestis. It persists in nature through transmission between its hosts (wild rodents) and vectors (fleas). During epizootics, the disease expands and spills over to other host species such as humans living in or close to affected areas. Here, we investigate the effect of large-scale climate variability on the dynamics of human plague in the western United States using a 56-year time series of plague reports (1950–2005). We found that El Niño Southern Oscillation and Pacific Decadal Oscillation in combination affect the dynamics of human plague over the western United States. The underlying mechanism could involve changes in precipitation and temperatures that impact both hosts and vectors. It is suggested that snow also may play a key role, possibly through its effects on summer soil moisture, which is known to be instrumental for flea survival and development and sustained growth of vegetation for rodents.

Author Notes

*Address correspondence to Nils C. Stenseth, PO Box 1066, Oslo 0316. E-mail: n.c.stenseth@bio.uio.no

Authors' addresses: Tamara Ben Ari, Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway, and Ecole Normale Superieure, Paris, France. Alexander Gershunov, Climate Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, E-mail: sasha@ucsd.edu. Rouyer Tristan, Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway, E-mail: rouyer.tristan@bio.uio.no. Bernard Cazelles, Ecole Normale Superieure, Paris, France, E-mail: cazelles@biologie.ens.fr. Kenneth Gage, Bacterial Zoonoses Branch, Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO, E-mail: klg0@cdc.gov. Nils Chr. Stenseth, Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway, E-mail: n.c.stenseth@bio.uio.no.

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