Warming climate may trigger this disease outbreak in Southern California

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In a new study, researchers found as climate change brings hotter weather to Southern California, coastal populations from San Diego to Santa Barbara may face an increased risk of contracting the West Nile virus and other mosquito-borne diseases.

The research was conducted by a team at the University of California, Berkeley, and elsewhere.

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.

The study team analyzed data on nearly 2 million mosquitoes that had been captured and tested for West Nile in Los Angeles between 2006 and 2016.

They then used machine learning to identify the landscape and climate conditions that influenced mosquito infection in different neighborhoods.

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

The results revealed a sharp transition, whereas temperatures shift between 70 to around 73 degrees Fahrenheit—the likelihood of capturing infected mosquitoes in L.A. neighborhoods increases dramatically.

Above this range, conditions become consistently favorable for transmission, and below this range, conditions are consistently unfavorable.

The results 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.

The team says with significant warming expected over the coming decades, a greater number of West Nile cases may be expected along the Southern California coast.

And while the data indicate that temperature plays a very important role, the researchers emphasize that many factors ultimately determine whether a West Nile outbreak will occur.

One author of the study is Nicholas Skaff.

The study is published in Proceedings of the Royal Society B: Biological Sciences.

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