Warming climate could lead to more West Nile in Southern California

The coastal areas of Southern California are often cooler than inland areas, and have some degree of protection against the West Nile virus. (Public domain photo)

It suggests that the coastal population from San Diego to Santa Barbara may face an increased risk of contracting the West Nile virus and other mosquito-borne diseases as climate change warms the weather in southern California. New research Headed by researchers at the University of California, Berkeley.

The West Nile virus, the most deadly mosquito-borne disease in America, has been a threat to the Los Angeles metropolitan area since its arrival in 2003. The virus infects mosquitoes and birds and spreads to humans by being bitten by infected mosquitoes.

The team analyzed data on nearly two million mosquitoes caught and tested in West Nile, Los Angeles between 2006 and 2016. Next, machine learning was used to identify landscape and climatic conditions that affected mosquito transmission in different regions.

They found that the transmission between caught mosquitoes was strongly associated with the average temperature in the neighborhood.

“Our data reveals a dramatic shift in the likelihood of catching infected mosquitoes in the LA region dramatically increasing as temperatures vary between 70 and about 73 degrees Fahrenheit.” Said Nicholas Scuff, the lead author of the study and a former postdoctoral researcher. Environmental Health Sciences, Department of Public Health, University of California, Berkeley. “Beyond this range, the conditions are always favorable for transmission, below which the conditions are always unfavorable.

result, Published today (Wednesday, August 5) Diary Minutes of Royal Society B, Helps explain why the coastal LA community (typical summer conditions are on the border of good and restraining temperatures) appears to be protected, but is vulnerable elsewhere.

Justin Remais, associate professor of environmental health sciences at the University of California, Berkeley, expects significant warming over the next few decades, with more West Nile cases on the coast of Southern California. I said yes.

“Coastal LA appears to be vulnerable to the climate warming of California expected by the mid-20th century.” Inland LA is less vulnerable to these changes because the climate is already favorable. It may be less susceptible, but as climate warming progresses towards the end of the century, temperatures in these areas can be very high.”

Studies have found that West Nile infection rates in mosquitoes are associated with differences in average daily temperatures. The coastal areas of LA, where the average temperature is between 67 and 72 degrees Fahrenheit, are more susceptible to mosquito infections than the central area where the average temperature is between 72 and 74 degrees F and the inland areas where the average temperature is above 74 degrees Fahrenheit. There were few. (Image source: Justin Remais)

Researchers emphasize that the risk of infection does not appear to increase significantly, especially on hot days or days. Rather, it is the warm temperatures that persist over the weeks that give the mosquitoes time to acquire the infection and infect it with a bird host species such as home finch.

“Our research suggests that it’s important to look at long-term temperatures rather than focusing on daily weather forecasts,” Scuff said. “If the coast of Los Angeles experiences warm temperatures of one or two months in the summer or early fall, it’s best to take extra precautions to avoid being bitten by mosquitoes. , It’s hot enough in the summer, and other factors will determine if a severe infection will occur there.”

The data also show that temperature plays a very important role, but researchers emphasize that many factors ultimately determine whether West Nile outbreaks occur.

“We can think of the preferred temperature range we have identified as a prerequisite. If nothing else works for the vector or virus, even at good temperatures, the infection may not yet occur,” Scuff said. Said. “For example, if the majority of susceptible birds in a region become infected in the previous year or two years due to a large outbreak, the herd’s immunity will be high and risk to people will be limited.”

“Predicting the transmission of infectious diseases mediated by animal hosts and vectors represents a complex puzzle,” Remais added. And what about the future? “

The research team includes Kuchen, Philip A. Colender, Jennifer R. Head, and Christopher M. Hoover from the University of California, Berkeley. Rachel ES Kremesh and Alexander Gerschnov of the Scripps Institute of Oceanography. Dennis P. Lettenmaier from UCLA. Jason R. Roll from Notre Dame University. Robert E. Snyder from the California Department of Public Health.

This work was supported by grants from the National Institute of Allergy and Infectious Diseases, the National Science Foundation, the Fogerty International Center for the National Institutes of Health, and the President of UC.

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