Sacramento County recently announced that mosquitoes were found carrying West Nile virus for the first time this year.
What's happening?
West Nile virus is a disease naturally hosted in birds; it's transmitted to humans and other animals via mosquitoes, per the World Health Organization.
And while California has had West Nile for years, cases are increasing. As of early June, there were already more than three times as many positive mosquito samples as the previous year, according to Medical Xpress.
The number of infected birds is growing too. The Sacramento-Yolo Mosquito and Vector Control District reported 26 dead birds as of July compared to last year's 16.
According to Medical Xpress, last year there were 54 human cases of the virus in Sacramento; two of those resulted in deaths.
Why is this concerning?
One reason this uptick is so worrying is that it can be ascribed to changes in global climate and temperature — and those are trending upward.
A study published in The Journal of Climate Change and Health found that the culex mosquito, which carries West Nile, responds "resiliently" to increased temperatures. This means, researchers concluded, that as temperatures continue to rise, "mosquito-borne disease is likely to be a continued threat."
Heat is also beneficial to viruses, as most of them replicate more quickly in hotter environments.
"As we expected, the very warm weather we've had recently increased the number of mosquitoes and accelerated virus activity," the control district manager Gary Goodman said in a news release. "It's important for residents to take these findings seriously and do everything they can to protect themselves."
These concerning trends aren't just limited to West Nile; more than 390 million people are already affected each year by the deadly dengue fever, and hundreds of thousands are infected with Zika, chikungunya, yellow fever, malaria, and more, according to the World Mosquito Program.
One study, published in Nature Microbiology, found that if temperatures continue rising at their current rates, an additional 2 billion people will be exposed to dengue in the coming decades.
What's being done about this?
Sacramento plans to increase mosquito trapping and monitoring in response to the positive samples. It also reported it would conduct ground spraying in an attempt to reduce the culex population.
Individuals can mitigate their exposure risk by draining or sealing off any stagnant water to prevent mosquitoes from breeding. And don't forget to inform others to do the same.
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