The San Joaquin County Mosquito & Vector Control District (District) vector-borne disease surveillance program continues to detect West Nile virus (WNV) throughout San Joaquin County. When getting outdoors as the summer-like weather lingers, use a repellent registered with the Environmental Protection Agency (EPA). These repellents, when used as directed on the label, effectively reduce mosquito bites.
“When it comes to protecting yourself from West Nile virus, skip the social media trends and unproven DIY remedies,” stated Sumiko De La Vega, the District Public Information Officer. “Use a proven effective method, by applying an EPA-registered insect repellent to prevent mosquito bites.”
In 2026 to date, the District has detected WNV in a total of 108 mosquito samples and seven dead birds while San Joaquin County Public Health has reported one human case. WNV has been active in San Joaquin County every summer since it was first detected locally in 2004, with activity declining in the fall. The virus survives in the wild bird population and is transmitted through the bite of Culex mosquito species, which are most active at dawn and dusk. In addition to regular treatments for mosquito larvae in water sources throughout the county, the District conducts targeted wide area truck-based or aerial mosquito control spray treatments in areas of WNV detection to reduce the risk of WNV transmission to the public.
Additionally, the invasive species, Aedes aegypti, is established in many residential neighborhoods throughout the county. While this species does not transmit WNV, it is an aggressive daytime biter that lives and reproduces close to homes. The females attach eggs to the sides of items throughout residential yards that hatch when exposed to water. Unlike native mosquitoes, this species can develop in as little as a bottlecap of water. District staff frequently find mosquito larvae in overwatered yards, yard and patio drains, drainage saucers under potted plants, buckets, and items exposed to sprinkler water.
The District conducts premise inspections; treats street drains, utility vaults, and other accessible sources; and conducts truck-based Wide Area Larvicide Spraying (WALS) in addition to conventional ultra-low volume (ULV) spray treatments. As this species most frequently develops in sources on private properties, the most effective method of reduction is for residents to weekly inspect and eliminate standing water sources in their yard: drain or remove items that collect water and apply screens to yard drains to keep mosquitoes out. Residents can also request a yard inspection or mosquito-eating fish (Gambusia affinis) for permanent water features by contacting the District. There is no fee for requesting District services.
Eliminate standing water on your property to prevent mosquito development. Sources can be as small as a bottle cap of water or as cryptic as an underground yard drain.
When outdoors, apply an insect repellent containing one of the following ingredients: DEET, picaridin, oil of lemon eucalyptus, PMD, or IR3535. Make sure to follow label directions.
Wear layered clothing with long pants and sleeves when outdoors, especially at dawn and dusk.
Exclude mosquitoes from your home with tight-fitting screens on doors and windows.
Contact your veterinarian for information on vaccinating equines against WNV.
Request a yard inspection or report a neglected swimming pool at www.sjmosquito.org.
Report dead birds to 1-877-WNV-BIRD (1-877-968-2473) or to www.westnile.ca.gov.
Follow the District on Facebook and Instagram @sjmosquitoandvector for regular mosquito prevention tips and updates.
To learn more about San Joaquin County Mosquito & Vector Control District, visit www.sjmosquito.org or contact them at 209-982-4675. The office at 7759 S. Airport Way, Stockton, is open Monday through Friday from 7 a.m. to 3:30 p.m.
