07/22/2026
Peak mosquito season is underway in Ventura County, and residents are encouraged to take steps to prevent mosquito breeding and protect themselves from mosquito bites.
West Nile Virus Activity in Ventura County
West Nile Virus (WNV) is established in Ventura County, and recent surveillance by the Ventura County Environmental Health Division has detected WNV activity in local birds and mosquitoes. Ventura County Public Health confirms that no human cases of West Nile Virus have been identified in Ventura County to date in 2026.
What Does It Mean When Birds or Mosquitoes Test Positive for West Nile Virus?
When a bird or mosquito tests positive for West Nile Virus, it means the virus is actively circulating in the local environment. Mosquitoes become infected when they feed on infected birds, which are the primary hosts of the virus. Infected mosquitoes can then transmit the virus to humans and other animals through their bites.
Positive detections in birds and mosquitoes serve as an early warning that the risk of human infection may increase. These findings help public health officials and our Vector Control team monitor virus activity and guide mosquito control efforts to reduce the risk to the community.
WNV-positive detections reported so far this season include birds collected in Ventura and Thousand Oaks, as well as a mosquito sample collected in Fillmore. Additional WNV-positive detections are expected throughout mosquito season as surveillance continues. To date, no human cases of West Nile Virus have been identified in Ventura County in 2026.
Latest West Nile Virus Updates
- May 27, 2026 – Local Bird Tests Positive for West Nile Virus in Ventura County
- June 9, 2026 – Second Local Bird Tests Positive for West Nile Virus in Ventura County
- July 8, 2026 – Mosquito Sample Tests Positive for West Nile Virus in Ventura County
- July 16, 2026 – Third Local Bird Tests Positive for West Nile Virus in Ventura County
For more information about West Nile Virus, including symptoms, transmission, prevention, and additional resources, visit our West Nile Virus Information Page
Know the Invasive Aedes aegypti Mosquito
In addition to native mosquito species that can transmit West Nile Virus, the invasive Aedes aegypti mosquito has become established in Ventura County.
Unlike many native mosquitoes, Aedes aegypti mosquitoes are aggressive daytime and nighttime biters that thrive in neighborhoods and around homes and businesses. They can breed in very small amounts of standing water—as little as a teaspoon.
Aedes aegypti mosquitoes are capable of transmitting viruses including dengue, Zika, chikungunya, and yellow fever. California has experienced locally transmitted dengue cases in recent years. Infected travelers can introduce dengue into areas where Aedes aegypti mosquitoes are present, creating the potential for local transmission.
Protect Yourself and Prevent Mosquito Breeding
Taking a few simple steps can help reduce mosquito breeding around your home and protect you and your family from mosquito bites.
The Ventura County Environmental Health Division and Ventura County Public Health recommend:
- Eliminate standing water in and around your home. Check places that can be easy to overlook, including plant saucers, children’s toys, basketball hoop bases, buckets, old containers left in the yard, tarps, drains, and other items that can collect and hold water. Remember, mosquitoes can breed in juts a teaspoon of standing water.
- Ensure doors and windows have tight-fitting screens without holes.
- Wear loose-fitting long sleeves and pants when mosquitoes are active, especially at dawn and dusk.
- Use an EPA-approved insect repellent containing DEET, picaridin, oil of lemon eucalyptus (PMD), or IR3535.
- Regularly inspect your yard and outdoor spaces for containers or other items that may collect water.
Watch: Simple Steps to Prevent Mosquitoes Around Your Home
Learn what you can do around your home to help eliminate mosquito breeding sources and protect yourself and your family from mosquitoes.
- Ventura County Vector Control – 2026 West Nile Virus Activity
- 5 Things That Actually Work To Keep Mosquitoes Away
Report Mosquito Activity
Residents can report mosquitoes or potential mosquito breeding sources in Ventura County by calling the Mosquito Complaint Hotline at (805) 658-4310.
The Environmental Health Division also provides mosquito-eating fish for non-maintained swimming pools, ornamental ponds, and similar water features. To request mosquito-eating fish, call (805) 662-6582.
Residents can report recently deceased wild birds for West Nile Virus testing by calling 877-WNV-BIRD (877-968-2473) or visiting the California West Nile Virus website.
For more information about mosquito prevention, surveillance, and control efforts in Ventura County, visit the Ventura County Environmental Health Division Vector Control Program webpage.