Protect Yourself from Mosquito-Borne Diseases in Southern California After Recent Heavy Rainfall

Recent heavy rainfall has created prime breeding grounds for mosquitoes throughout Southern California, leading to concerns of an influx in the mosquito population and the potential transmission of diseases such as West Nile Virus and St. Louis Encephalitis Virus. Steve Vetrone, director of scientific-technical services for the Greater L.A. County Vector Control District, warns that unmaintained swimming pools are one of the biggest problems they see in terms of mosquito production.[0] With the recent rainfall, these pools have taken on a lot of new water and bacteria, providing the perfect environment for mosquitoes to breed.

Experts warn that the abundance of water and increasing temperatures will lead to an increase in the mosquito population, and with it, the risk of contracting potentially deadly diseases.[1] As the temperature rises, the proliferation of invasive mosquito species may pose problems. The West Nile virus causes a neurological disease including high fever, tremors, paralysis, or even death in less than 1% of infections. A less serious version of the illness, affecting 20% of those infected, may cause a fever, headache, and body aches lasting for weeks.[2] Approximately 1 in 5 people who are infected with West Nile Virus will develop symptoms such as fever, headache, body aches, joint pains, vomiting, diarrhea, or rash. Less than 1 percent will develop a serious neurologic illness such as encephalitis or meningitis, and about 10 percent of people who develop neurologic infection due to West Nile virus will die, according to the CDC.

County residents are being urged to take steps such as clearing away standing water on their property, such as outdoor containers, and cleaning out clogged roof gutters.[3] Large drains that hold water are also a possible source of mosquito activity, and placing screens under drain covers could prevent mosquitoes from breeding. In addition, residents are being advised to use repellents containing DEET, picaridin, oil of lemon eucalyptus, IR3535, or Para-menthane-diol as an active ingredient, in accordance with CDC recommendations. It has been demonstrated that repellents with an EPA-registered active component are efficient.[3]

Local vector control officials say mosquito season could be somewhat delayed this year due to the recent cool and wet weather.[4] However, if the weather dries up over the next couple of months, agricultural production could start sooner, and so would mosquito season.[5] Crews have been sent into the field to reduce mosquito populations by spraying a diluted solution of Vectobac onto bodies of water where the pests can be seen moving around near the surface.[6] The bacteria present in it are natural and selectively target mosquito larvae.[6]

Residents are being urged to help reduce mosquitoes and mosquito diseases by regularly cleaning out bird baths or animal water bowls, keeping rain gutters clear of leaves and debris, and dumping and scrubbing (every 3 days) any outdoor containers holding water such as pet dishes, birdbaths, fountains, and kiddie pools. The Marin-Sonoma mosquito control district recommended repellents that contain DEET, picaridin, oil of lemon eucalyptus, IR3535, or Para-menthane-diol as an active ingredient, in accordance with CDC recommendations.[1]

In conclusion, it is important for residents to take proactive measures to prevent the breeding of mosquitoes on their property, and to use repellents when spending time outdoors. With the recent rainfall creating prime conditions for mosquito breeding, it is crucial to stay vigilant and take necessary precautions to protect oneself and one's community from potentially deadly diseases.

0. “Epic California rains expected to take one more bite: Masses of mosquitoes”, 6 Apr. 2023,

1. “Heavy rains, warmer weather bring increase in mosquitos” The Turlock Journal, 12 Apr. 2023,

2. “Storms, standing water are recipe for spreading West Nile disease in Stanislaus region” Modesto Bee, 11 Apr. 2023,

3. “As California storms abate, here are the projections for mosquitoes” San Francisco Chronicle, 9 Apr. 2023,

4. “Cold temperatures push back mosquito season” KRCR, 4 Apr. 2023,

5. “Is California’s next health concern blood-sucking mosquitoes? All this water spells trouble” Sacramento Bee, 3 Apr. 2023,

6. “Crews get ahead of rains-fueled boom of mosquito larvae at coastal Orange County wetlands” Los Angeles Times, 8 Apr. 2023,

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