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VENTURA — Following last week’s rainfall and with warmer temperatures expected this week, the Ventura County Environmental Health Division (Division) is urging residents to eliminate standing water around their homes and properties to prevent mosquito breeding and reduce the risk of mosquito-borne diseases, including West Nile virus (WNV). The reminder comes as the California Department of Public Health reports West Nile virus activity at a five-year high statewide.
Standing water left in outdoor containers can quickly become a breeding source for mosquitoes. In as little as seven days, mosquito eggs can hatch, larvae can develop, and adult mosquitoes can emerge. With mosquito activity continuing into the fall, recent rainfall, and warmer temperatures may contribute to increased mosquito populations throughout Ventura County.
Aedes aegypti, an invasive mosquito capable of transmitting dengue, chikungunya, Zika, and yellow fever viruses, has been detected throughout Ventura County this fall, including in Camarillo, Fillmore, Oak Park, Ojai, Oxnard, Santa Paula, Simi Valley, Thousand Oaks, and Ventura. This aggressive mosquito can breed in as little as a teaspoon of water, and its eggs can survive in dry containers until rainfall creates favorable breeding conditions.
Culex quinquefasciatus, commonly known as the southern house mosquito, is a primary vector of West Nile virus in the region. In 2026, the Division has collected this species in mosquito traps at rates significantly higher than the five- and ten-year averages. Eliminating standing water following rainfall can help reduce populations of mosquitoes capable of transmitting West Nile virus.
The Division monitors and controls approximately 2,700 mosquito breeding sources throughout Ventura County. Residents are encouraged to support mosquito control efforts by regularly inspecting their properties and eliminating standing water from buckets, plant saucers, toys, tarps, and other outdoor containers. Objects that collect water should be emptied, discarded, or properly stored to prevent mosquito breeding.
The Ventura County Environmental Health Division recommends the following precautions:
- Eliminate standing water sources in and around homes.
- Ensure doors and windows have tight-fitting screens without holes.
- Wear loose-fitting long sleeves and pants when mosquitoes are active.
- Use EPA-registered insect repellents containing DEET, picaridin, oil of lemon eucalyptus, PMD, or 2-undecanone.
Residents can also:
- Report mosquito activity or standing water by calling the Mosquito Complaint Hotline at (805) 658-4310 or submitting a report online at eco.vcrma.org.
- Request mosquito-eating fish for ornamental ponds and water features by calling (805) 662-6582.
- Report dead birds for West Nile virus testing by calling 1-877-WNV-BIRD (1-877-968-2473) or visiting westnile.ca.gov.
For more information about mosquito prevention and control in Ventura County, residents can visit the Environmental Health Division’s Vector Control Program webpage.