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New Mosquito Fogging in Santa Clara, Sunnyvale Aug. 3


Another year, another round of mosquito fogging to prevent the spread of West Nile virus-positive mosquitoes. The County of Santa Clara Vector Control District will fog parts of Sunnyvale and Santa Clara on Thursday, Aug. 3. Zip codes including 94085, 94086, 94087 and 95051 will be fogged starting around 10 p.m. and finishing around midnight. Vector control says mosquitoes in the Sunnyvale area tested positive for West Nile virus and the area must be treated to reduce the adult mosquito populations.

Vector Control uses trucks to drive through affected areas and fog. The fogging is often done during the summer in affected areas, as was the case last summer.

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 is detected, the District takes the added step of conducting adult mosquito control treatments. It is crucial that the District conduct mosquito control treatments upon finding a positive mosquito. Any delay in the application would present an imminent threat to public health and safety, exposing the public to potential injury, or even death, caused by a vector. The adult mosquito control treatments reduce the mosquito population in the area, which decreases the risk of a West Nile virus-human infection.


It is normal to see an increase in West Nile virus during the summer and early fall because mosquitoes thrive in warm weather. 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 West Nile virus-transmitting mosquito populations.

Notice is being sent directly to the public in Santa Clara and Sunnyvale who live in the treatment ZIP codes through AlertSCC and to those who subscribe to Nextdoor. General notice is 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 questions from the public, Monday–Friday, on its dedicated West Nile Virus Hotline at (408) 282-3114, from 7:30 a.m. to 3:30 p.m. Questions can also be submitted by email to

The affected area is centered at South Wolfe Road and Old San Francisco Road in Sunnyvale. It is bordered by East California Avenue and East Arques Avenue at its north and El Camino Real and Remington Drive at its south. Lawrence Expressway, Willow Avenue, Timberpine Avenue, Sugarpine Avenue, Henderson Avenue and Poplar Avenue make up the eastern border. Azure Street, Sunnyvale-Saratoga Road, South Mathilda Avenue, South Taaffe Street, South Frances Street, North Murphy Avenue and Jackson Street make up the western border.

There is no need to relocate from Sunnyvale and Santa Clara 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 members and pets inside during the approximately four-hour treatment, with windows and doors shut. In the morning, the insecticide quickly breaks down when exposed to 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. All control materials utilized in our mosquito control program are approved by the Environmental Protection Agency for use in public areas 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 2022, there were 15 human West Nile virus-related deaths; 2015 was a record year for fatalities in the state with 55 deaths.

West Nile virus 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. People 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 any 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 at (408) 918-4770 or submit an online service request.


1 Comment
  1. Buchser Alum 9 months ago

    Thank you for covering this so we have the warning. Now I know what night to not take a late evening walk and to keep the windows closed.

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