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Sunnyvale West Nile Positive Mosquitoes Found

The County of Santa Clara Vector Control District has confirmed the presence of West Nile virus-positive mosquitoes in a small area of Sunnyvale (ZIP Codes 94086 and 94087). Weather permitting, this area will be treated to reduce adult mosquito populations with the use of truck-mounted equipment on Friday, Sept. 9, starting around 10 p.m. and concluding a few hours later.

The County of Santa Clara Vector Control District has treated Sunnyvale and the Sunnyvale area several times this summer. It sprayed areas in Sunnyvale and Cupertino on Aug. 25 and areas in Santa Clara and Sunnyvale in July.

The District’s mosquito management program largely focuses on preventing mosquitoes from reaching the adult biting stage by proactively targeting immature stages of mosquitoes found in standing water. When a mosquito with West Nile Virus (WNV) is detected, however, the District takes the added step of conducting adult mosquito control treatment to reduce the mosquito population in the area, which decreases the risk of a WNV-human infection.


It is normal to see an increase in West Nile virus during the summer because mosquitoes thrive in hot weather. Although mosquitoes need water at each stage of life, they are still able to thrive during the drought conditions the state and county are seeing now.

The District has a dedicated surveillance program to detect the presence of diseases like West Nile virus, St. Louis encephalitis and western equine encephalitis, all of which are transmitted through the bite of infected mosquitoes. The data collected through surveillance is used to predict locations that are more likely to have these disease-transmitting mosquitoes.
The District has been conducting truck-mounted treatments regularly since 2003 to successfully reduce WNV-transmitting mosquito populations. The District will be adhering to requirements and recommendations from the County of Santa Clara Public Health Department for COVID-19.

Notice is being sent directly to the public in the treatment ZIP codes through AlertSCC and to those who subscribe to Nextdoor neighborhood networks. General notice is being provided on various social media platforms – including Facebook, Instagram and Twitter (@SCCVCD) – and to those subscribed to the District’s mosquito treatment notifications.

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

Area of Treatment

The specific details of the operational areas are:

  • Treatment date: Friday, Sept. 9, around 10 p.m., for approximately four hours
  • Supervisorial Districts: 3
  • Cities: Sunnyvale
  • Centered at: Chopin and Rembrandt drives
  • Bordered by:
  • North – Bartlett Avenue, South Wolfe Road, Starbush Drive, Sugarpine Avenue, Henderson Avenue, Spinosa Drive, Rubis Drive, Russet Drive, Hollenbeck Avenue, South Mathilda Avenue, South Taaffe Street, Murphy Avenue, South Sunnyvale Avenue, Deodar way, South Fair Oaks Avenue and North Fair Oaks Avenue
  • East – Cedar Avenue, East Kifer Road, East Evelyn Avenue, Paintbrush Drive, Sheraton Drive, Princeton Drive, Hyde Park Drive, Danforth Drive, state Route 82, West Iowa Avenue, West McKinley Avenue and East Washington Avenue
  • South – Henderson Avenue, Sage Hen Way, Teal Drive, Oriole Avenue, Mure Lane, Meadowlark Lane, Longspur Avenue, Heron Avenue, Blackhawk Drive, Sunnyvale-Saratoga Road, Prince Edward Way, Cordilleras Avenue, Hollenbeck Avenue, Sesame Drive and Royal Ann Drive
  • West – Castleton Way, Dunford Way, Exmoor Way, Inverness Way, Humewick Way, Alberta Avenue, Cheyenne Drive, Cascade Drive, West Fremont Avenue, Vanderbilt Drive and Torrington Drive
  • ZIP Codes affected: 94086 and 94087

Interactive map:

There is no need to relocate during the treatment. Mosquito treatments pose minimal risk to people, pets, animals and the environment when applied by a licensed vector control professional following label instructions. Those who would like to take extra precautions can keep family and pets inside during the approximately four-hour treatment, with windows and doors shut. By sunrise, the insecticide will quickly break down with the sunlight. Since the District applies insecticides at ultra-low volume (ULV), individuals aren’t likely to breathe or touch anything that has enough insecticide on it to be harmful. Those with chemical sensitivities may want to consult their physicians for additional recommendations. All control materials utilized in our mosquito control program are approved by the Federal and State environmental protection agencies and are widely used by vector control agencies throughout California.

For more information on the products used for this adult mosquito control treatment, including the safety data sheet, insecticide label and a list of our most frequently asked questions, visit our website at For additional information on adulticides, visit the Centers for Disease Control and Prevention’s website at For information on West Nile virus activity in California, go to

Health Effects of West Nile Virus

Since West Nile virus arrived in California in 2003, more than 7,000 people across the state have contracted the disease; nearly 400 of those cases were fatal. In 2021, there were 12 human WNV-related deaths; 2015 was a record year for fatalities in the state with 55 deaths.

WNV infection does not cause symptoms in most people; however, for some individuals it can cause fever, headache, body aches and, in severe cases, significant neurological damage or death. Individuals with certain chronic medical conditions (such as diabetes, high blood pressure, cancer and kidney disease) and the elderly are most at risk for serious complications.

The public can assist in preventing the spread of West Nile virus by taking the following prevention measures.

On your property:

  • Inspect for standing water on a weekly basis.
  • Drain or turn over anything that can hold water, such as flowerpots, planter bases, pet dishes, buckets and old tires.
  • Clean items like bird baths and pet bowls once a week to remove mosquito eggs.
  • Clear debris from rain gutters on a regular basis to allow water to flow.
  • Properly screen rain barrels, cisterns and irrigation drains to prevent mosquito access.
  • Fix leaky water faucets and broken sprinkler heads and avoid overwatering lawns and plants.
  • Ensure window and door screens are in good condition with no holes or tears and are tight-fitting.
  • Ensure swimming pool water level is adequate for proper circulation and filtration.
  • Free mosquitofish can be requested online at for placement in neglected pools/spas, ornamental ponds, water troughs and other artificial bodies of water. For more information on our mosquitofish program, visit

Outdoor Activities:

  • Limit outdoor activities during dusk and dawn – these are the times when the mosquitoes that transmit WNV are most active.
  • If spending time outdoors, dress in long-sleeve shirts and long pants, preferably in light colors – mosquitoes are mostly attracted to dark colors.
  • Apply insect repellent that contains DEET, IR3535, or Oil of Lemon Eucalyptus, always following label instructions.

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 submit an online service request.


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