The West Nile Virus was confirmed in Fresno, California this year in early June. A study from the University of California, Berkley suggests that as climate change worsens, warm weather in Southern California will increase the risk of contracting mosquito-borne diseases.
Recently published in the journal Proceedings of the Royal Society B, the paper analyzed West Nile (WN) transmission in Los Angeles, where it first arrived in the metropolitan area in 2003. This particular virus has been one of the deadliest mosquito-borne illnesses across the entire country.
The Berkley team reviewed data of about 1.8 million mosquitos that were tested for WN between 2006 and 2016. Using machine learning, they identified how climate conditions and landscape affected infection rates in several neighborhoods.
Between 70 and 73 degrees Fahrenheit, the researchers saw a 'sharp transition' in finding infected mosquitos from L.A. neighborhoods. Nicholas Skaff, a former postdoctoral scholar at UC Berkeley's School of Public Health, said, 'Above this range, conditions become consistently favorable for transmission, and below this range, conditions are consistently unfavorable.'
Warm Temperatures in the L.A. Coast
Professor Justin Remais said that they expect the L.A. coastal region, including San Diego and Santa Barbara, to become more vulnerable to mosquito populations carrying various diseases. Significant warming in this region due to climate change will 'push coastal climates more consistently into the favorable zone' for mosquitos to thrive.
Skaff said that as coastal L.A. temperatures stay warm during the summer and early fall, it is best to take extra precautions to avoid mosquito bites. 'Inland parts of L.A. are almost always sufficiently hot during the summer, so other factors end up determining whether intense transmission occurs there,' he said.
Aside from warm temperatures, transmission still occurs even if the climate is unfavorable, said Skaff. Birds can also get infected with West Nile. Skaff explained that if most of the birds in L.A. have been infected within the last two years, herd immunity may be high from the large outbreak.
Read Also: Mosquitos Carrying Dengue, Zika, Yellow Fever Would Be More Prevalent by 2030, Study Warns
Mosquito Populations Worldwide
Moreover, global warming has also allowed mosquito populations to travel further north into states where they previously could not survive due to cold weather. States such as Michigan, New Hampshire, and Connecticut have been capturing mosquitoes and ticks infected with West Nile and Jamestown Canyon Virus.
Another study from Imperial College London and Tel Aviv University predicted that mosquitoes will be prevalent in southern Europe by 2030 - carrying diseases like dengue, yellow fever, and Zika virus. Based on the current rates of greenhouse gas emissions will allow mosquitos to reproduce 4.4% times more every ten years by 2050.
'Predicting the transmission of infectious diseases carried by animal hosts and vectors represents a complex puzzle,' added Remais, 'and machine learning can pick up patterns in vast epidemiological and ecological datasets that help us understand why certain people and neighborhoods are at the highest risk, as well as what the future holds.'
Read Also: Dengue and Other Mosquito Diseases Are Slowly Making Their Way North
