West Nile Virus Activity Still Present In Marin & Sonoma Counties

Release date: 
Nov 7
Cotati, CA-The Marin/Sonoma Mosquito and Vector Control District (MSMVCD) announced that West Nile virus activity is still being detected in parts of Sonoma County. This past week two dead birds tested positive for the virus; one from Rohnert Park and the other from Santa Rosa. In addition to the dead birds, a sentinel chicken from Cloverdale tested positive for antibodies to West Nile virus.
West Nile virus activity has been steadily decreasing over the past several weeks and should continue to diminish as the cooler weather takes hold. While the threat of West Nile virus transmission has always been extremely low in the winter months due to the cold weather, residents need to be aware that mosquitoes are still present.
"There are over twenty species of mosquitoes in both counties, and they are all fairly unique with respect to where and when they lay their eggs," stated Piper Kimball, Scientific Programs Director for MSMVCD. "Some species are most active in the spring and summer while others are more active in the fall and winter months."
With backyards being the number one source for mosquito production, residents are urged to be proactive by mosquito proofing their yards prior to the wintertime rains. Anything that can hold water for more than five days can become a major source for mosquito production. Being diligent and proactive now will not only help to reduce mosquito issues during the winter, it can help to lessen the amount of adult mosquitoes that may hatch next spring.  

 Here a few tips to help reduce mosquito production:

  • Check septic tank lids to ensure a tight seal and repair any visible cracks.
  • Screen septic tank vent pipes using a fine mesh screen.
  • Inspect and remove standing water that may have collected under your home.
  • Be sure all rain barrels are screened and in good repair.
  • Recycle old tires or store in a sheltered area, away from the rain.
  • Eliminate standing water in rain barrels, old tires, buckets, kiddie pools or any other item that can hold water for more than five days.
  • Report mosquito problems, neglected swimming pools, or any area that could be producing mosquitoes at www.msmosquito.com or 1-800-231-3236.
  • Residents interested in staying informed about district activities are encouraged to follow MSMVCD on  twitter and  facebook.

A backyard checklist is available at  www.msmosquito.com to help residents identify areas that are often overlooked. See the chart below for all 2013 West Nile Virus activity both counties.


2013 West Nile Virus Activity in Marin & Sonoma Counties





Dead Birds

Mosquito Pools

Sentinel Chickens

Dead Squirrels












The Marin/Sonoma Mosquito and Vector Control District is an independent special district committed to protecting public health from mosquitoes and vector-borne disease. All programs and services are funded through benefit assessments and property taxes. Services are provided to all residents in Marin and Sonoma counties.