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First Detection of West Nile Virus for 2023

Cotati, CA.  August 4, 2023 – The Marin/Sonoma Mosquito and Vector Control District has confirmed finding the first dead bird infected with West Nile virus (WNv) for 2023. The American Crow was collected near Culpepper Dr. and Maria Dr. in Petaluma and is the first detection of West Nile virus activity for the 2023 season.

"This positive dead bird serves as a crucial reminder of the endemic nature of West Nile virus in our region,” said Nizza Sequeira, Public Information Officer for the Marin/Sonoma Mosquito and Vector Control District. "We strongly encourage the public to continue to look for and eliminate stagnant water in their yards, introduce mosquitofish to permanent ponds, and take personal protection measures against mosquito bites,” stated Sequeira.

District staff will continue to trap, test, and monitor the abundance of adult mosquitoes in the area where the positive dead bird was found. In addition, vector control technicians are inspecting all documented sources of mosquito production, searching for new sources, and conducting mosquito control operations as necessary.  

The Marin/Sonoma Mosquito and Vector Control, along with the California Department of Public Health, recommend using a repellent with one of the following active ingredients: DEET, picaridin, IR3535, Para-menthane-diol (PMD), or oil of lemon eucalyptus (OLE).

Other ways to protect yourself from mosquitoes and mosquito bites include:

  • Stock permanent water features with mosquitofish (free from the District)
  • Be sure to properly screen and/or secure lids on rain barrels or water storage containers
  • Do not over-water lawns
  • Clean out bird baths and animal water bowls at least twice a week
  • Keep swimming pools and hot tubs properly chlorinated
  • Make sure that septic tank lids are properly sealed and vent pipes are screened
  • Report dead birds to

Visit to report mosquito issues or to learn more about mosquitoes and vector-borne disease.

The Marin/Sonoma Mosquito and Vector Control District's programs and services are funded through property taxes and benefit assessments and are provided to all residents in Marin and Sonoma counties at no additional charge. 

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