County Plans Fogging Operation in San Jose after West Nile Virus Detected in Local Mosquitoes

West Nile Virus is back in San Jose, and here comes the fog.

Santa Clara County’s Vector Control District began chemically fogging last month after  finding mosquitoes that tested positive for West Nile virus in west and south San Jose.

County officials plan to fog from 11pm Thursday to 2am the next day in affected neighborhoods to prevent spread of the virus, which can become fatal (53 died of the disease in 2015). The county Vector Control District uses trucks that spray a mist of mosquito-killing pesticide. Not everyone is a fan.

The fogging will take place in the following areas: north to Ironwood Drive and Altino Boulevard; east to Hillcap Avenue, Snell Avenue and Kingspark Drive; south to Branham Lane and Chynoweth Avenue; and west to Almaden Expressway.

The county has used a chemical called Zenivex E4 since 2005 during West Nile virus season, from May through September. Vector control officials urge people in targeted neighborhoods to close their windows and doors and keep pets inside while the fogging trucks roll through.

Door hangers notifying residents of the upcoming fogging went out last week. Online notifications were sent through AlertCC and Nextdoor as well as on Yahoo! Groups, Twitter and the county vector control app.

Vector control staff will be on call during the fogging to answer any concerns or issues by phone—408.918.4770—and email.

Below is the press release from SCCvcd:

The Santa Clara County Vector Control District (SCCvcd) has confirmed that adult mosquitoes collected from the 95125 and 95136 ZIP code areas of the city of San José have tested positive for West Nile virus (WNV) after our initial fogging on June 23, 2016.  The detection of mosquitoes infected with WNV has prompted the scheduling of a mosquito re-fogging in the northern portion of the treated area (in brown in the map below) and a new fogging treatment in a surrounding area (in blue) in an effort to prevent human cases of WNV.  Weather permitting, the ground fogging operations are scheduled for 11 p.m. on Thursday, July 7, and will conclude a few hours later.

Door hangers notifying residents of the scheduled fogging will be distributed in the affected neighborhoods starting on Saturday, July 2.  Notice is being sent directly to those area residents in the affected ZIP codes through AlertSCC and to those who subscribe to Nextdoor neighborhood networks. General notice also is being provided on various social media platforms used by the SCCvcd including Yahoo Groups (SCCvector), Twitter (SCCvcd), and the SCCvector app.

On Thursday and Friday, July 7 and 8, vector control staff will answer questions via a dedicated phone line/voicemail (800.314.2427) from 8 a.m. to 4 p.m. Questions can also be submitted by email [email protected].

The specific details of the operational areas are:

Fogging date: Thursday, July 7, from 11:00 p.m. to approximately 2:00 a.m. the following morning, Friday, July 8

Supervisorial District: Portions of District 1 & District 2

Cities: San José

Centered at: Guadalupe Pkwy. (87) & West Capitol Expressway

Bordered by:

o  North – Ironwood Drive, Altino Boulevard

o  East – Hillcap Avenue, Snell Avenue, Kingspark Drive

o  South – Braham Lane, Chynoweth Avenue

o  West – Almaden Expressway

Zip codes affected: 95125, 95136

Map at:

“West Nile virus positive mosquitoes discovered along the north side of the last fogging zone (June 23) has prompted a fogging to further reduce disease transmission there,” said Santa Clara County Vector Control District’s Surveillance Manager, Dr. Noor Tietze. “Independence Day is a time of outdoor celebrations and watching fireworks. Play it safe and take measures to avoid mosquito bites.”

During the fogging operation, there is no need to relocate. However, those who wish to minimize exposure for family or pets may wish to close windows and remain inside during the fogging period which is typically three hours in duration. Individuals who have chemical sensitivities may want to consult their physicians.

Health Effects of West Nile Virus

Since the arrival of WNV to California in 2003, 5,588 people across the State have contracted the disease; 229 of those cases were fatal.  2015 was a record year for fatalities in the state with 53 deaths.

WNV infection does not cause symptoms in most people, but in some individuals it can cause fever, headache, body aches, and in severe cases, significant neurological damage or death.  Adults older than 50 years and individuals with certain chronic medical conditions such as diabetes, high blood pressure, cancer, and kidney disease are most at risk for serious complications.

Residents can play a strategic role in preventing the spread of West Nile Virus.  It is important to remain vigilant by taking practical steps to eliminate standing water around the home.

Some practical measures against mosquito bites are:

At home:

  • Mosquitoes lay eggs in water.  DRAIN or DUMP standing water weekly.
  • Drain, remove, or turn over anything that can hold water: flowerpots, planter bases, bird baths, toys, cans, rain gutters, pet dishes, buckets, and old tires. Fix leaky water faucets and sprinklers.
  • Screens on doors and windows should be tight-fitting and in good repair.
  • Do not let your swimming pool water fall below the pump circulation area. Free mosquitofish placement can be requested through the SCCvcd for neglected pools or ornamental ponds.


  • Limit outdoor activities during DUSK & 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 following label instructions.

Contact the Vector Control District if you are being bothered by mosquitoes or know of a potential mosquito-breeding source.

For free assistance with mosquito control, WNV, or other vectors, residents can contact the District office by calling 408.918.4770 or fill out a service request online at


  1. SCCvcd provides some information about the risks of WNV, but not a word about the risks to humans and pets of the poison it will be spraying into the air; not even an estimate of the drift vector of the poison they will be spraying; not even a vague disclaimer about the safety of the poison to humans and pets. For all we know, the cure is worse than the disease; more people may be harmed by the poison than might be harmed by the mosquitoes. Are we being lulled into a sheepish acceptance of this sort of spraying in order to prepare us to blindly accept a lethal dose of something else down the line? We won’t know until it’s too late, will we? Baahh, sheep to the slaughter. The link in paragraph 2 mentioned a lawsuit filed by Ms. Jensen in 2015 that is on appeal, but SJI did not do a follow up to let us know the status of the appeal. Calling the SCCvcd hot line will probably get you someone reading the party line from a script. Perhaps the person responding will really be in Bangalore or Mumbai, like the software tech support people.

  2. “Perhaps the person responding will really be in Bangalore or Mumbai, like the software tech support people.”

    Should I infer that you expect your SCC tech support people should live in the County they serve? But didn’t you also want them to move if they can’t afford to live here? Maybe Bangalore and Mumbai are more affordable and corporations and residents have taken your advice.

    Just saying….

  3. West Nile Virus is a fraud designed to sell pesticides by inciting FEAR into the public. The original research claiming to discover it violated Koch’s postulates and renders it invalid.The encephalopathies are more likely due to other infectious microbes, toxic chemicals, and vaccine reactions. The zika virus is also a fraud. It does not cause microcephaly, pesticides like pyriproxyfen do. Keith Howe, D.C.

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