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Sonoma County Gazette
Sonoma County Mosquitoes

Sonoma County Mosquitoes Test Positive for West Nile Virus

Sep 15, 2017


First sample of West Nile Virus positive mosquitoes for 2017

The Marin/Sonoma Mosquito & Vector Control District (District) announced today that a group of mosquitoes tested positive forWest Nile virus(WNv) in Sonoma County. The WNv positive mosquitoes were collected in the vicinity of Wilfred Avenue and Whistler Avenue in Rohnert Park. 

"The results of our surveillance data suggest an elevated risk for disease transmission to residents in the vicinty,"  said Angie Nakano, Scientific Programs Manager for the Marin/Sonoma Mosquito and Vector Control District. "It is extremely important that residents protect themselves from mosquito bites by employing personal protection measures such as wearing long sleeves and long pants, and applying an effective insect repellent to exposed skin." 
Repellents that contain an active ingredient which has been registered with the U.S. Environmental Protection Agency (EPA) have been proven to be most effective when applied according to the instructions on the label.  
District personnel will be conducting additional surveillance and control work in the area. Residents are urged to report stagnant water sources and mosquito problems to the Marin/Sonoma Mosquito and Vector Control District. 

Simple ways to help reduce exposure to mosquitoes and lessen the risk of WNv:

  • Avoid being outdoors during peak mosquito activity (dawn and dusk).
  • Check and maintain all window and door screens.
  • Report mosquito problems or any area that could be producing mosquitoes at or 1-800-231-3236.
  • Report dead birds to the West Nile virus hotline at 1-877-968-2473 or online at
  • Wear mosquito repellent when outdoors at dusk and dawn. Use a repellent containing one of the following active ingredients: DEET, Picaridin, oil of lemon eucalyptus, or IR3535.

Which mosquito repellents work best? CDC recommends the use of products containing active ingredients which have been registered with the U.S. Environmental Protection Agency (EPA) for use as repellents applied to skin and clothing.Of the products registered with the EPA, those containing DEET, picaridin, IR3535, and some oil of lemon eucalyptus and para-menthane-diol products provide longer-lasting protection.EPA registration means that EPA does not expect the product to cause adverse effects to human health or the environment when used according to the label.



Mosquitoes are small, blood-feeding flies (Order: Diptera, Family: Culicidae). Most species are only 1/8 - 1/4” long. Adult mosquitoes have two wings and a long needle-like mouth (called a proboscis). Immature stages of mosquitoes are aquatic and do not resemble the adults. Mosquito larvae are elongated and often have a long respiratory siphon, while pupae are comma-shaped and have two smaller breathing tubes.   

Life cycle & habitat: 

Mosquitoes develop in a wide range of aquatic habitats; please view our Mosquito Production Sources Gallery to see a variety of places where mosquitoes commonly lay their eggs. Some species of mosquitoes lay large numbers of eggs directly onto standing water, while others deposit eggs in areas that periodically flood. Mosquitoes progress through four life stages: egg, larvapupa and adult. Aquatic mosquito larvae hatch from eggs and develop into pupae. The pupae emerge from the water as adults. Warm temperatures generally encourage faster development, with some mosquitoes developing from egg to adult in approximately one week. Please see our Mosquito Life Cycle Gallery to see pictures of all life stages of mosquitoes. 

Impact on human health: 
  • Adult female mosquitoes may bite humans or other vertebrates (including pets, livestock and wildlife) to obtain the blood required for egg development.
  • Bites cause skin irritation and may become infected especially if the bite is scratched.
  • Worldwide, mosquitoes are known to transmit a wide range of pathogens, including virusesfilarial nematodes, and protozoans such as the parasite that causes malaria.
  • Locally, mosquitoes are known to transmit West Nile virus (WNV) to humans and dog heartworm to certain animals.


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