Atherton: More mosquitoes found infected with West Nile virus

Additional mosquito fogging scheduled Thursday night

After fogging mosquitoes in one Atherton neighborhood over the weekend, additional adult mosquitoes carrying West Nile virus have been found in Atherton, prompting the scheduling of more fogging Thursday night.

The San Mateo County Mosquito and Vector Control District announced the find Aug. 3 and said the fogging would take place from 9 p.m. Thursday, Aug. 4, to 5 a.m. Friday, Aug. 5.

The newly discovered disease-carrying mosquitoes were collected in the vicinity of Selby Lane and Stockbridge Avenue, following an adult mosquito fogging in a neighboring area in the early morning on July 30, the district said.

“Mosquitoes collected from last week's treatment area were clear," said Megan Caldwell, the district's education and outreach officer, “but we found infected mosquitoes in another area nearby. We're very concerned about the risk of West Nile in this area."

Ms. Caldwell urged local residents take precautions to avoid mosquito bites.

Seven dead birds infected with West Nile virus had been found in the nearby area over a two-week period between July 6 and July 20, prompting the initial testing of mosquitoes.

Ms. Caldwell said the treatment will be with Zenviex E4 (4% etofenprox) applied with a truck-mounted ultra-low-volume fogger at a rate of around one ounce per acre.

The treatment area is primarily residential, with approximate boundaries of Selby Lane, Montgomery Avenue and Hull Avenue on the north, Alameda de las Pulgas on the west, Camino al Lago, Faxon Road and Atherton Avenue on the south and Austin Avenue and Elena Avenue on the east.

For more information or assistance with a mosquito problem, call the district at (650) 344-8592, Monday through Friday from 8 a.m. to 4:30 p.m. or visit its website.

While infected adult mosquitoes are capable of transmitting West Nile virus to humans, many people who are infected show no symptoms, Ms. Caldwell said. Adults over age 50 are at higher risk of severe illness if infected.

The primary hosts of West Nile virus are birds, but humans, horses and other animals can become infected if bitten by an infected mosquito. It cannot be spread from person to person.

Precautions that can be taken to avoid mosquito bites, include:

● Keep doors and windows closed or tightly screened, and inspect screens regularly for openings.

● Wear insect repellent and/or long sleeves and pants outdoors, especially at dusk and dawn when mosquitoes are most active.

● Dump and drain standing water where mosquitoes may breed.

The district says the treatment does not pose any significant risk to humans, pets, gardens, wildlife or the environment and no special precautions are needed before or during the fogging.

District technicians are also going to be in the area working to prevent more mosquitoes from hatching, especially by finding and treating or eliminating any standing water where mosquitoes may be developing.

Mosquitoes will again be collected in the area after the treatment is complete. If post-treatment mosquito samples are carrying West Nile virus, additional adult mosquito control treatments may be necessary.

Reports of dead birds are an early indication that West Nile virus is circulating in the environment. Residents may report fresh carcasses of birds or tree squirrels on or by calling 877-WNV-BIRD (877-968-2473).

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3 people like this
Posted by dianab
a resident of Portola Valley: Central Portola Valley
on Aug 3, 2016 at 12:14 pm

Please stop fogging. The neurotoxicity of this pesticide is worse for us than the mosquitos. How many humans have been infected with West Nile Virus in Atherton? The numbers of people being exposed to a neurotoxic chemical may outnumber those who have been infected with West Nile.

Like this comment
Posted by TERRY
a resident of Menlo Park: Fair Oaks
on Aug 3, 2016 at 12:44 pm

i have already sent a comment that on Sat. 7/30 .... I found approx. 20 dead and dying bees.... I have never seen that before. One of our trees that has been filled with bees --- on Sat. morning only 2-5 were seen flying around the tree --- when that tree is usually filled with bees Our location was sprayed on Friday night and Sat. Morning.
-- It makes me wonder and be very concerned ... that we were told this 'SPRAY' would only effect the Mosquitoes !!!!! Something does NOT seem right.

Like this comment
Posted by Barbara Wood
Almanac staff writer
on Aug 3, 2016 at 3:11 pm

Barbara Wood is a registered user.

Here is a response from Megan Caldwell of the mosquito control district about the chemical possibly killing bees:

The product we use is an insecticide and bees are insects, so the active ingredient itself is toxic to bees in some situations. However, the likelihood of bees being affected by overnight ULV mosquito control is very low because, like us, they’re inside asleep at night. We apply the product at an extremely low concentration – just an ounce or so per acre – and we use the ULV fogger to disperse it in a mist so that it breaks down mostly in the air rather than settling on surfaces. By the time bees emerge from their hives in the morning, most of the insecticide is gone.

We also maintain communication with the San Mateo Beekeepers’ Guild. We’ve asked them to let their members know when and where we’ll be treating, and to let us know if they notice any problems. We have yet to hear from any of our local beekeepers that their hives have been affected over the course of several dozen treatments and three summers. I’m certain that if a beekeeper in the treatment area had experienced any significant loss, they would be calling us directly.

We’ll definitely follow up on this if the resident contacts us, but it doesn’t sound like they have. Without any further information, we have no way of knowing where this was, if the insects were actually bees, when it happened, etc.

District phone: 650-344-8592
or website Web Link

Like this comment
Posted by Stella
a resident of Atherton: other
on Aug 3, 2016 at 3:20 pm

West Nile here, Zika coming?

"At least 12 babies in the United States have already been born with the heartbreaking brain damage caused by the Zika virus. And with that number expected to multiply, public health and pediatric specialists are scrambling as they have rarely done to prepare for the lifelong implications of each case."

Obama wants funding. Republicans blocked Zika funding.


"Juan Fiol, Trump’s vice chairman for Miami-Dade County, is betting most voters don’t care enough about Zika to warrant Trump’s attention.

“We have bigger mosquitoes to squash than Zika — like ISIS, the national debt, Iraq, and Afghanistan,” Fiol said, pounding his fist on the bar during an interview at a Trump party in downtown Miami. “We have a wall to build to keep the illegals out. We have so many other issues that are more important than this.”

He called Clinton “sophomoric” for “taking on such an insignificant issue.”"

And that, my friend, is why your campaign is getting it's backside kicked.

2 people like this
Posted by concerned
a resident of Atherton: other
on Aug 10, 2016 at 8:27 am

Ugh. There were about two dozen dead bees and wasps on my patio after the fogging.
Hello people- are pollinators are going extinct...doesn't anyone care about the food supply?

Like this comment
Posted by farm puddles
a resident of Atherton: Lindenwood
on Aug 10, 2016 at 9:34 am

I killed 4 skeeters just on my legs while outside last night in Lindenwood. Folk gotta clean up their yards, pools of water, broken irrigation pipes and puddles.


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