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Second Mosquito Sample Tests Positive for West Nile Virus

Cotati, CA October 18,2021- The Marin/Sonoma Mosquito and Vector Control District confirmed today that a sample of adult mosquitoes collected in a trap, has tested positive for West Nile virus (WNV). This is the second mosquito sample to test positive for WNV in Sonoma County this year. The mosquito sample was collected from the vicinity of Santa Rosa Avenue and Burt Street in the city of Santa Rosa.

“District staff will continue to monitor the distribution and abundance of adult mosquitoes in the area where the positive mosquito sample was collected,” stated Nizza Sequeira, Public Information Officer. “The District will also continue to test viable adult mosquito samples collected in the area for WNV. In the meantime, we ask that residents report mosquito problems to our office and take personal protection measures such as wearing an effective mosquito repellent when engaging in outdoor activities.”

Vector control technicians are also looking for new sources of mosquito production in the area, inspecting known sources, and conducting mosquito control as necessary. Along with reporting mosquito biting issues, the District is urging residents to reduce mosquito production sites in their yards by removing items holding stagnant water. 

Simple ways to reduce the risk of West Nile virus:

  • Store containers upside down, covered, or in a sheltered area.
  • Cover rain barrels or other water storage containers tightly with a fine mesh screen (1/16 inch).
  • Screen septic tank vent pipes with a fine mesh screen (1/16 inch). Check tank lids for cracks and repair if needed.
  • Keep rain gutters clear of leaves and other debris.
  • Check and maintain all window and door screens.
  • 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. 

Please contact the Marin/Sonoma Mosquito & Vector Control District (707-285-2200) for information and/or assistance in resolving mosquito-related problems. Visit for more information regarding mosquito and vector control.


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