FAQs about Mosquito Fogging in Los Altos-Mountain View

West Nile Virus fogging? We asked so you would have some answers. The Santa Clara County Vector Control District 'fogged' for mosquitoes infected with the West Nile virus in ZIP codes 94024 and 94040, covering Los Altos, LAH, and Mountain View.


Patch interviewed Russell Parman of the Santa Clara County Vector Control District, which that it will be applying an insecticide-laced 'fog' to kill infected mosquitoe on late Thursday night and early Friday morning in Los Altos and Mountain View area ZIP codes of 94024 and 94040. You can follow them on Twitter @sccvcd

Patch:    Why did the county fog Thursday night?

Russell Parman: This was the first fogging of 2012. Since the introduction of West Nile virus in 2004, the Santa Clara County Vector Control District monitors constantly for signs of West Nile-infected mosquitoes, just as its counterparts. Last week significant numbers of mosquitoes (one in 75 mosquitoes) were found the Los Altos Mountain View area. Fogging is done as soon as possible, after the voluntary notification is done. 

Patch:    How did the vector control district determine the area?

Parman: The fogging area is in a one-mile radius of the “hot spot” where the infected mosquitoes were found.

Patch:    How long did the fogging go on for?

Parman: The fogging started about 11 p.m. and generally lasts until 2 a.m. or 3 a.m., depending on conditions. If winds are less than 1 m.p.h. or more than 10 m.p.h., the trucks stop fogging.

Patch:    Can you tell me where the fogging trucks went and when?

Parman: There are four trucks equipped with fogging equipment, and the area was divided into four quadrants. Each driver decided on the route. They travelled at their own pace, usually at 15 m.p.h., depending on the density of the housing on the street.

Patch:    What’s in the fog?

Parman: We used two different insecticides, according to Environmental Protection Agency standards: Pyrenone 25-5 insecticide or Pyronyl 525, which are equivalent and found in flea and pet shampoos, and Zenivex E4, which was recently registered. The fogging machines are calibrated to a tight range of 20 microns (one micron is 1/1000th of a milliliter). See the Santa Clara County Vector Control District’s website for more detail. 

Patch:    Are the insecticides dangerous?

Parman: Only to mosquitoes, in this really miniscule concentration, because their bodies are so small. The fine fog should not even kill moths, because they are larger. The extremely fine mist should evaporate or settle out. We are generally conservative. The industry standard is to do three foggings. This area is not as hot as the Central Valley or Southern California, and we do one fogging.

Patch:    If I am sensitive, should I leave the area?

Parman: You should talk to your doctor if you have sensitivities.

Patch:    Why didn’t we get more notice?

Parman: We worked as fast as we could. We're balancing people's desire to get ample notice with the desire to get the mosquitoes to be knocked out as soon as possible. Getting the word out, despite the array of technology available, is still difficult because people sometimes ignore flyers and emails.

The mosquitoes were collected Aug. 1, and the test results came back Aug. 3. A plan was confirmed, flyers were ordered, then the press release was competed Aug. 7. The urgency is, when we find infected mosquitoes in field, we know the cycle is amplifying. That means just about every mosquito that was on the infected bird will have the virus and we want to break the amplification cycle. And the mosquitoes are very efficient carriers from the birds to us.

Patch:    How much in advance are you required to give us notice?

Parman: We’re actually not required to give notice, but Santa Clara County has a policy of doing so. We may be alone in the state in having this practice. You can sign up for email updates and now follow us on Twitter.

Patch: How bad can West Nile virus be?

Parman: There is West Nile disease, which is a severe neural invasive form. The neural invasive form is potentially fatal, particularly to those over 50 and have diabetes. There is evidence suggesting that those with compromised immune system may get it more severe form. Typical symptoms include fever, headache, body aches and in severe cases, significant neurological symptoms.

There is also West Nile fever, a “mild” form for which people some people can be out of work for as long as as 16 days. Some of these milder ones people never go to the doctor. Since it arrived in California in 2004, there have been 16 cases and no fatalities. 

Editor's Note: To see the list of street boundaries within which fogging will occure from 11 p.m. Thursday to early Friday, see our story about the The .


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