Warming climate may trigger more West Nile outbreaks in Southern California

https://www.eurekalert.org/pub_releases/2020-08/uoc--wcm080520.php

News Release 5-Aug-2020
University of California - Berkeley

As climate change brings hotter weather to Southern California, coastal populations from San Diego to Santa Barbara may face an increased risk of contracting West Nile virus and other mosquito-borne diseases, suggests a new study led by researchers at the University of California, Berkeley.

West Nile virus is America's deadliest mosquito-borne disease and has been a threat to the Los Angeles metropolitan area since it arrived in 2003. The virus is harbored by mosquitos and birds and is most commonly spread to humans through the bite of an infected mosquito.

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They found that infection among captured mosquitoes was strongly associated with the average temperature in the neighborhood.

"Our data revealed a sharp transition, where -- as temperatures shift between 70 to around 73 degrees Fahrenheit -- the likelihood of capturing infected mosquitoes in L.A. neighborhoods increases dramatically," said Nicholas Skaff, the lead author of the study and a former postdoctoral scholar in environmental health sciences at UC Berkeley's School of Public Health. "Above this range, conditions become consistently favorable for transmission, and below this range, conditions are consistently unfavorable."

The results, published today (Wednesday, Aug. 5) in the journal Proceedings of the Royal Society B, help explain why coastal L.A. communities -- where typical summer conditions hover right at the boundary between favorable and inhibitory temperatures --- seem to be protected some years, yet vulnerable in others.

With significant warming expected over the coming decades, a greater number of West Nile cases may be expected along the Southern California coast, said Justin Remais, associate professor of environmental health sciences at UC Berkeley.

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