Data from: 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.