San Joaquin County just logged its first confirmed West Nile virus detection of the season, and it turned up right where officials were expecting trouble: in a mosquito trap in the Delta. After routine mosquito surveillance flagged the positive sample, vector control and public health officials reminded residents to clear out standing water, stick with EPA-approved repellents, and be extra cautious at dawn and dusk as mosquito activity climbs with the warmer weather.
Where It Was Found
According to the state’s West Nile Virus dashboard on WestNile.ca.gov, San Joaquin County has recorded one West Nile virus-positive mosquito sample so far this year, as reflected in the June 22, 2026 weekly update. The site notes that this is the county’s first mosquito indication for 2026, landing amid new positives popping up across the Central Valley.
Local Details And Reaction
San Joaquin County Mosquito & Vector Control District officials told reporters that one of 80 traps set by the district tested positive, and that the sample came from a trap in the Upper Jones Tract, about 10 miles west of Stockton. “This is the western encephalitis mosquito - it’s one of the species that can transmit West Nile virus here in our county,” spokesperson Sumiko De La Vega said, as reported by CBS Sacramento.
What The District Is Doing
The district says it offers residents several tools to keep mosquito numbers in check, from traps to free mosquitofish, and posts spray alerts when adult mosquito counts or virus detections reach levels that trigger treatment. Details on the mosquitofish program and how to request services are available on the San Joaquin County Mosquito & Vector Control District website.
How To Reduce Your Risk
Public health guidance has not changed: dump and drain standing water, cover birdbaths and outdoor containers, wear repellent with DEET or Picaridin, and limit outdoor time at dawn and dusk when mosquitoes are most active. State and local officials also ask residents to report dead birds to 1-877-WNV-BIRD and to contact the district if they notice heavy mosquito activity, as outlined by WestNile.ca.gov.
