Testing finds no additional West Nile virus carrying mosquitoes in Atherton

Mosquito district says residents should still take precautions

The county's mosquito control district says that no West Nile virus carrying mosquitoes were found in testing after a second round of mosquito fogging treatment on Aug. 4.

The San Mateo County Mosquito and Vector Control District has twice fogged to kill adult mosquitoes in Atherton and nearby areas in recent weeks after finding mosquitoes carrying West Nile virus. The district said the fogging reduced the population of adult mosquitoes in the area by 70 percent. Work to control mosquito larvae in the area continues.

"Although we didn't find infected adult mosquitoes this week, residents are encouraged to continue to take basic precautions against mosquito bites," said Megan Caldwell, the district's public health education and outreach officer.

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

Some local residents have said they have found dead bees and other insects after the fogging, but Ms. Caldwell said that although the chemical is an insecticide and can kill other insects, that because the spraying takes place at night when most other insects are not active, and is in such a dilute concentration, it should not affect them.

To avoid mosquito bites, the district suggests residents:

● Apply insect repellents that contain DEET, picaridin, oil of lemon eucalyptus, or IR 3535, following label instructions.

● Make sure screens on doors and windows are tight fitting and without holes or tears to keep out mosquitoes.

● Eliminate standing water and containers that can hold water outdoors.


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