West Nile virus and climate change.

Abstract

West Nile virus (WNV) is a mosquito-borne flavivirus with a global distribution that is maintained in an enzootic cycle between Culex species mosquitoes and avian hosts. Human infection, which occurs as a result of spillover from this cycle, is generally subclinical or results in a self-limiting febrile illness. Central nervous system infection occurs in a minority of infections and can lead to long-term neurological complications and, rarely, death. WNV is the most prevalent arthropod-borne virus in the United States. Climate change can influence several aspects of WNV transmission including the vector, amplifying host, and virus. Climate change is broadly predicted to increase WNV distribution and risk across the globe, yet there will likely be significant regional variability and limitations to this effect. Increases in temperature can accelerate mosquito and pathogen development, drive increases in vector competence for WNV, and also alter mosquito life history traits including longevity, blood feeding behavior and fecundity. Precipitation, humidity and drought also impact WNV transmissibility. Alteration in avian distribution, diversity and phenology resulting from climate variation add additional complexity to these relationships. Here, we review WNV epidemiology, transmission, disease and genetics in the context of laboratory studies, field investigations, and infectious disease models under climate change. We summarize how mosquito genetics, microbial interactions, host dynamics, viral strain, population size, land use and climate account for distinct relationships that drive WNV activity and discuss how these dynamic and evolving interactions could shape WNV transmission and disease under climate change.