SANTA CLARA COUNTY, Calif. (KRON) — Sunnyvale and Santa Clara will be receiving a treatment to reduce West Nile Virus (WNV) positive adult mosquito populations at 10 p.m. on Monday, July 11, according to a press release from the County of Santa Clara Vector Control District (VCD).

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WNV-positive mosquitoes have been confirmed in areas of Sunnyvale and Santa Clara, according to Santa Clara County officials. The mosquitos were discovered thanks to a dedicated surveillance program that aims to detect the presence of diseases like WNV. When a WNV-positive mosquito is found, the VCD begins an adult mosquito control treatment to lower the mosquito population, which in turn reduces the risk of a human contracting WNV.

The VCD has orchestrated treatments regularly since 2003, and will be adhering to all requirements from the County of Santa Clara Public Health Department for COVID-19. Door hangers have been placed at some homes in the affected areas since July 5. The District is also using social media to inform people in the area. There is no need to relocate during the treatment.

Vector Control staff members will be able to answer questions from the public Monday through Friday via the dedicated West Nile Virus Hotline (408) 282-3114, from 7:30 a.m. to 4:00 p.m. Questions can also be submitted by email to

The mosquito treatments don’t pose a large risk to people, pets, animals, or the environment when used correctly. If you would like to take extra precautions you can keep family and pets inside during the treatment time, and shut all windows and doors. The insecticide will break down in the sunlight once the sun rises.

If you would like more information about what products will be used, please visit the website If you would like more information on WNV in California visit

Details about the treatment location can be found below:

Treatment date: Monday, July 11, around 10 p.m., for approximately three hours

Supervisorial Districts: Districts 3 and 4
Cities: Sunnyvale and Santa Clara
Centered at: Ajax Drive and Joshua Way
Here’s a map of the area:

This is an image of the treatment area for Sunnyvale and Santa Clara
Santa Clara, Sunnyvale Treatment Zone Map

ZIP Codes affected: Parts of 94085, 94086, 94087 and 95051

Interactive map:

Tips for combatting mosquitos on your property:

  • Dump or drain standing water weekly. Mosquitoes need stagnant water to lay their eggs and spend three out of four life stages in water.
  • Drain, remove or turn over anything that can hold water, such as flowerpots, planter bases, bird baths, toys, cans, rain gutters, pet dishes, buckets and old tires. Fix leaky water faucets and sprinklers. For more information on water conservation and mosquito prevention, visit
  • Screens on doors and windows should be tight-fitting and in good condition.
  • Do not let your swimming pool water fall below the pump circulation area. Free mosquitofish can be requested online at for placement in neglected pools or ornamental ponds. For more information on our mosquitofish program, please visit

Tips for avoiding West Nile Virus during outdoor activities:

  • Limit outdoor activities during DUSK and DAWN to prevent mosquito bites. Those are the times when the mosquitoes that transmit WNV are most active. 
  • If you need to go outside in an area where mosquitoes are active:
    • Dress in long-sleeve shirts and long pants, preferably in light colors
    • Apply insect repellent approved by the Environmental Protection Agency, following label instructions. For more information on mosquitoes, visit

Contact the County of Santa Clara Vector Control District if you are being bothered by mosquitoes or know of a potential mosquito-breeding source. For free assistance with mosquito control or other vectors, residents can contact the District office main line at (408) 918-4770 or fill out a service request online at