Drought and immunity determine the intensity of West Nile virus epidemics and climate change impacts.
The effect of global climate change on infectious disease remains hotly debated because multiple extrinsic and intrinsic drivers interact to influence transmission dynamics in nonlinear ways. The dominant drivers of widespread pathogens, like West Nile virus, can be challenging to identify due to regional variability in vector and host ecology, with past studies producing disparate findings. Here, we used analyses at national and state scales to examine a suite of climatic and intrinsic drivers of continental-scale West Nile virus epidemics, including an empirically derived mechanistic relationship between temperature and transmission potential that accounts for spatial variability in vectors. We found that drought was the primary climatic driver of increased West Nile virus epidemics, rather than within-season or winter temperatures, or precipitation independently. Local-scale data from one region suggested drought increased epidemics via changes in mosquito infection prevalence rather than mosquito abundance. In addition, human acquired immunity following regional epidemics limited subsequent transmission in many states. We show that over the next 30 years, increased drought severity from climate change could triple West Nile virus cases, but only in regions with low human immunity. These results illustrate how changes in drought severity can alter the transmission dynamics of vector-borne diseases.
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, 1156 High St, Santa Cruz, CA 95064, USA sara.paull@colorado.edu.|Research Applications Lab, National Center for Atmospheric Research, 3450 Mitchell Ln, Boulder, CO 80301, USA.
Sara H
0000-0001-5589-9568
SH
Paull
Department of Earth and Planetary Sciences, Northwestern University, Evanston, IL 60208, USA.|Department of Earth System Science and Woods Institute for the Environment, Stanford University, Stanford, CA 94305, USA.
Daniel E
DE
Horton
Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Moetasim
M
Ashfaq
Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Deeksha
D
Rastogi
Wadsworth Center, New York State Department of Health, Slingerlands, NY 12159, USA.|School of Public Health, Department of Biomedical Sciences, SUNY, Albany, NY 12201, USA.
Laura D
LD
Kramer
Department of Earth System Science and Woods Institute for the Environment, Stanford University, Stanford, CA 94305, USA.
Noah S
NS
Diffenbaugh
Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, 1156 High St, Santa Cruz, CA 95064, USA akilpatr@ucsc.edu.
A Marm
0000-0002-3612-5775
AM
Kilpatrick
D000818:Animals; D057231:Climate Change; D009033:Culicidae / Q000821:virology; D055864:Droughts; D058872:Epidemics; D006801:Humans; D007303:Insect Vectors / Q000821:virology*; D014901:West Nile Fever / Q000453:epidemiology*; D014902:West Nile virus
Culex; disease ecology; global warming; nonlinear temperature–disease relationship; vector-borne disease