Additional West Nile Virus Activity Detected

Release date: 
Aug 14

Cotati, CA-The Marin/Sonoma Mosquito & Vector Control District announced today that additional West Nile virus (WNV) activity in Marin and Sonoma counties has been detected. This week, mosquitoes trapped in the vicinity of Millbrae Ave. and Langer Ave. in Santa Rosa tested positive for WNV. This area has seen virus activity in past years. Adult mosquito control operations were conducted early this morning to reduce the adult mosquito populations and break the transmission cycle. Additional surveillance and trapping will be conducted in the area to assess the mosquito populations and virus activity. 

Residents are urged to report mosquito problems in their areas and to reduce mosquito production sites in their yards by removing standing water on a regular basis.  Most importantly, residents should use personal protection measures against mosquito bites. Wearing long sleeved shirts, long pants and applying an effective repellent to exposed skin will help reduce the risk of WNV transmission from an infected mosquito.

In addition to the positive mosquito sample, two dead birds have tested positive for WNV this week; an American crow collected from the vicinity of Jean Marie Dr. in Santa Rosa and a western scrub-jay collected from the vicinity of Leafwood Hts. in Novato. 

2014 West Nile virus activity:

Marin County: 3 dead birds and 3 mosquito samples have tested positive for West Nile virus to date.

Sonoma County: 12 dead birds and 4 mosquito samples have tested positive for West Nile virus to date.

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

  • Eliminate standing water in rain barrels, old tires, buckets, kiddie pools or any other item that can hold water for more than 72-96 hours. 
  • Check septic tank lids to ensure a tight seal and repair any visible cracks.
  • Screen septic tank vent pipes using a fine mesh screen.
  • Report mosquito problems, neglected swimming pools, or any area that could be producing mosquitoes at or 1-800-231-3236.
  • Stock backyard ponds or other permanent water features with mosquitofish. The fish are free and can be delivered or simply picked up at the District office.
  • 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. 
  • Residents interested in staying informed about district activities are encouraged to follow MSMVCD on twitter and facebook.

West Nile virus is a mosquito-borne disease that is spread by the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds. Infected mosquitoes can then spread the disease to humans and other animals.

Less than 1% of people (about 1 in 150) infected with WNV develop serious illness. These cases may last for extended periods of time, result in permanent neurological damage and may be fatal.  

Approximately 20% of people (about 1 in 5) infected with WNV experience mild symptoms that may include fever, headache, body aches, nausea, rashes, swollen lymph nodes and vomiting. Approximately 80% of people (about 4 out of 5) infected with WNV do not show any symptoms.