West Nile Virus Found Near La Mesa, San Diego: What Vector Control Is Doing About It

SAN DIEGO, CA — San Diego County is taking a hard look at mosquitoes after the discovery of West Nile virus in mosquitoes in the Rolando neighborhood of San Diego in late June. County crews will conduct pesticide treatments in the area this week.

According to the county vector control, the treatments will be "ultra-low volume," truck-mounted pesticide mist.

They will impact all 4,000 parcels of land in the community, which straddles the border of San Diego and La Mesa.

Workers will conduct "truck treatments" using AquaDuet — a pesticide approved by the Environmental Protection Agency that poses low risks to humans and pets, according to a statement from the county.

The treatments are scheduled to take place from 1 a.m. to 6 a.m. on Wednesday through Friday, depending on conditions.

Mosquitoes collected in that area on June 24 tested positive for the virus. Follow-up surveillance and testing revealed additional virus-positive mosquitoes in the vicinity, according to a recent statement.

"While the treatments pose a low risk to people and pets and the pesticide dissipates in roughly 20 to 30 minutes, residents may wish -- as a precaution -- to stay inside, keep pets and pet bowls inside, and close windows during the treatment," the statement read.

Normal activities can be resumed 30 minutes after the treatment is completed.

NOTE: Beekeepers and those with insects kept outdoors are encouraged to shelter hives and habitats during treatments.

The positive tests mark the first time mosquitoes have tested positive in San Diego County since 2023. Four dead birds have also tested positive this year. There have been no reported human cases in San Diego County this year.

The largely avian disease can be transferred to humans, where it can manifest in a headache, fever, fatigue, nausea, rash, or swelling, and even serious illness or death.

In 2024, the County reported 2 cases of West Nile Virus. By far, one of the more devastating years for West Nile Virus was 2015, when 44 San Diego County residents tested positive for West Nile virus, and six died, according to the county.

To avoid virus-carrying mosquitoes, county guidelines recommend finding and disposing of standing water to eliminate breeding grounds.

Additionally, preventing mosquito bites is crucial in avoiding the virus. Tips include using DEET insect repellent, wearing long sleeves and pants, and securing windows and screens in homes.

If residents see a stagnant pool or other mosquito breeding grounds — or find dead birds like hawks, jays, crows and owls —they are encouraged to contact the county Vector Control Program at 858-694-2888 or vector@sdcounty.ca.gov/