First Dead Bird Tests Positive for West Nile Virus in Sonoma County

Release date: 
Jul 19

Cotati, CA - The Marin/Sonoma Mosquito and Vector Control District (District) confirmed finding the first dead bird infected with West Nile virus (WNV) in Marin and Sonoma counties for 2012. The bird, an American crow, was found near Magnolia Avenue and Keokuk Street in Petaluma and submitted for testing on July 11, 2012.

"It's no surprise to find a dead bird that is positive for West Nile virus," said Nizza Sequeira, Public Relations Director of the Marin/Sonoma Mosquito and Vector Control District.

The presence of West Nile virus is increasing throughout California, especially in areas where temperatures are high. Standing water coupled with spikes in temperature, creates an ideal situation for rapid mosquito production and elevated levels of the virus within the mosquito, making transmission to humans, birds and animals more likely.

"The mild weather has been in our favor this year, but should we see a sharp increase in temperatures for an extended period of time, we will likely begin to see more West Nile virus activity in the area," stated Sequeira.

The District works diligently year-round to protect residents from mosquitoes and vector-borne disease. During the summer months additional staff is hired to meet the increase in demand for our services, which span over 2000 square miles. Increased surveillance efforts are already underway in the vicinity of the positive dead bird. Adult mosquito surveillance traps have been set in the area to assess the abundance and species of mosquitoes and to evaluate whether or not they are carrying the virus. All known mosquito breeding sources are being monitored, and technicians are scouring the area in search of other sites that may be producing mosquitoes.

The most difficult issue the District faces is dealing with the mosquito breeding sites found in residents' backyards. Common mosquito production sites include ponds, bird baths, septic tanks and even rain-harvesting barrels that haven't been screened correctly. Foreclosed homes with neglected swimming pools pose another risk, as they can produce over 1 million mosquitoes each. The bottom line is that if something looks like it could produce mosquitoes, it probably is, and therefore should be reported to the District.

"We can't get rid of the mosquitoes if we don't know you're having a problem," said Sequeira. Residents are urged to report mosquito problems, neglected pools, or any area they suspect may be producing mosquitoes to the District at 1-800-231-3236.

Residents can help reduce the threat of WNV in the following ways:

  • Eliminate standing water in rain barrels, old tires, buckets, kiddie pools or any other item that can hold water for more than a week.
  • Report mosquito problems, neglected swimming pools, or any area that could be producing mosquitoes.
  • 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.
  • 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.

West Nile virus (WNV) 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 (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.

For more information or to report mosquito problems contact the Marin/Sonoma Mosquito and Vector Control District at 1.800.231.3236 or visit 

Report dead birds to the West Nile virus Hotline at 1-877-968-2473 or online at

The Marin/Sonoma Mosquito and Vector Control District is an independent, special district committed to protecting public health from mosquitoes and mosquito-borne diseases. All programs and services are funded through property taxes and are provided to all residents of Marin and Sonoma counties. For more information about us please visit our website at or call 1-800-231-3236.