VENTURA, Calif. — Strong winter storms, summer heat, and tropical storm Hilary have produced an influx of Aedes mosquitoes in California, which bite daily, laying eggs in some regions in the first reported cases human cases of West Nile virus over the years.
The statewide increase brings to 153 reports of West Nile so far, more than double last year, according to the California Department of Public Health. It shows a nationwide pest infestation following increased rainfall in some parts of the country and has raised concerns about other mosquito species, prompting people to drain standing water and create other steps.
Culex mosquitoes carry the virus and can be found throughout California, according to the state’s public health department. In June, officials confirmed that three dead birds were infected with West Nile in Simi Valley, Thousand Oaks, and Ventura.
Public health officials said the birds could be signs of an increased risk of the virus, although no infected birds have been found.
The virus usually does not cause illness and sometimes causes flu-like symptoms. In less than 1% of cases, it can cause neurological conditions such as meningitis and encephalitis.
“People need to be on their toes. They need to worry about mosquito bites,” said Dr. Robert Levin, a health official in Ventura County, where the first case of West Nile virus in four years was revealed Thursday.
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‘Final push’
California’s development has been marked if not a perfect storm, an offensive one.
First comes the deluge of rain early in the year and triple-digit heat in July and August. Hilary, the storm that became a tropical storm, provided the exclamation point by dumping several inches of rain on pools, flower pots, arroyos, and other breeding grounds.
“It’s the last push. It gives the mosquitoes what they need,” said Cary Svoboda, head of a mosquito control program at the Ventura County Environmental Health Division.
Zapping in self-defense
Culex mosquitoes can be black or light brown. They usually bite from dusk to dawn.
Aedes aegypti mosquitoes are small and black with white stripes on the back and legs. They bite aggressively during the day, which raises concern because they have the potential to carry diseases such as Zika, dengue, chikungunya, and yellow fever, although there have been no reports of that occurring in California.
Over the years, Aedes mosquitoes have been found in Los Angeles and Kern counties but not in Ventura. That changed in 2020 when the invasive species, also known as the yellow fever mosquito, was discovered in many local communities.
Reports of Aedes aegypti have jumped this year, Svoboda said.
Reduce risks
Besides bug zappers, vector control, and public health officials are pushing people to take other steps:
- Clear standing water from buckets, barrels, saucers under flower pots and other containers.
- Clean properties of toys and other items that can hold water.
- Change the water in pet dishes and bird baths.
- Repair broken screens on doors and windows.
- Wear insect repellent outdoors, especially at dusk and dawn.
- Report mosquito activity to a hotline at 1-805-658-4310.
- For mosquito fish for use in pools and ornamental ponds, call 1-805-662-6582.
