September 3, 2026

West Nile Virus Positive Mosquito Detections Surge in the San Gabriel Valley 

Public health officials urge residents to take preventative measures against mosquito bites over the holiday weekend 

A close-up of a mosquito feeding on human skin, showing its body and proboscis against a blurred green background.

West Covina, Calif. (September 3, 2026) – The San Gabriel Valley Mosquito and Vector Control District (SGV Mosquito) has detected 105 West Nile virus (WNV) positive mosquito samples across cities and unincorporated areas within its service area, year-to-date. While WNV is endemic to the region, disease activity has surpassed the district’s five-year average signaling a need for residents to take extra precautions while outdoors during peak mosquito activity hours.

A person inspects water in a drain using a flashlight and a small container, possibly for environmental testing.

West Nile virus is spread through the bite of an infected Culex mosquito which is most active at dusk and dawn. Vector control technicians are actively monitoring and controlling known sources and canvassing for additional sources in communities with elevated mosquito activity. Additionally, district staff are conducting enhanced surveillance and increasing awareness and education around mosquito prevention and protection. 

A comprehensive list of WNV detections can be found on the district’s website.

“Although current WNV activity is higher than usual, our teams are purposely equipped to deal with this challenge,” said Director of Scientific Programs Tristan Hallum. “We strongly encourage residents to tip out any stagnant water around their homes, toss out any unused containers that can collect water, and protect themselves with mosquito repellent when outdoors during this holiday weekend.” 

While WNV disease activity fluctuates year-to-year, local and state agencies are also observing higher than average activity. Visit VectorSurv Maps for a comprehensive look at this year’s WNV activity throughout Los Angeles County and California.

There is no human vaccine or cure for West Nile virus; residents must be proactive at preventing mosquito-transmitted diseases through prevention and protection. Follow the tips below to reduce mosquito activity to stay healthy and bite free: 

  • Eliminate standing water in clogged rain gutters, rain barrels, discarded tires, buckets, watering troughs, or anything that holds water for more than a week.
  • Ensure that swimming pools, spas, and ponds are properly maintained. 
  • Change the water in pet dishes, birdbaths, and other small containers weekly.
  • Report neglected swimming pools in your neighborhood to your vector control district. 
A woman helps a young boy with something, possibly applying lotion or insect repellent, against a backdrop of greenery and a brick wall.

Follow the tips below to prevent mosquito bites:  

  • Apply mosquito repellent to exposed skin before going outdoors and reapply as recommended on the label. 
  • Wear insect repellent containing CDC and EPA approved active ingredients: DEET®, Picaridin, IR3535, or Oil of Lemon Eucalyptus.
  • Wear light-colored, long-sleeved shirts and long pants. 

For more information about West Nile virus activity in the San Gabriel Valley, residents can contact the district at 626-814-9466, online at SGVmosquito.org, or on social media @SGVmosquito.

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Media Contact

Anais Medina Diaz, Director of Communications

amedinadiaz@sgvmosquito.org |. 626-814-9466