CONCORD, CALIFORNIA - The Contra Costa Mosquito & Vector Control District (District) has reported six more groups of mosquitoes and six more dead birds have tested positive for West Nile virus (WNV) in Contra Costa County. The mosquitoes were from Palm Tract (near Knightsen), Discovery Bay, and Brentwood. Five of the six birds that tested positive were picked up in the city of Brentwood and one was from Antioch. This brings the total number of virus positive dead birds so far this year in Contra Costa County to seven.

Certain types of birds may carry WNV. When a mosquito bites an infected bird, the mosquito can become infected and transmit the virus to another bird or a person through a mosquito bite.

While the risk level for West Nile virus is currently elevated in Brentwood, it is not necessarily restricted to that area, according to the District's Scientific Program Manager Steve Schutz, Ph.D.

"Residents countywide should be taking precautions against mosquito bites," said Schutz.  "We appreciate members of the public reporting dead birds - this helps our agency identify where the virus hot spots may exist. Additional surveillance and control are being conducted where the mosquitoes and birds were collected to mitigate the risk of disease transmission. We advise residents to use an insect repellent when mosquitoes are present and to dump out any standing water on their property.”

Adult mosquito control may be necessary to decrease the number of infected mosquitoes and risk of WNV transmission in the area.

Contra Costa County residents can reduce the risk of WNV by taking the necessary steps to prevent mosquitoes by:

  • Dumping or draining standing water. Mosquitoes develop from egg to adult in water
  • Defending yourself - use repellents containing DEET, Picaridin, or Oil of Lemon Eucalyptus
  • Keeping swimming pools chlorinated and filtered because just one neglected pool can produce up to 1 million mosquitoes and affect people several miles away
  • Avoiding the outdoors when mosquitoes are present, typically dawn and dusk
  • Report dead birds to the state hotline by phone at (877) WNV-BIRD (968-2473) or online

Since 2005, 66 people in Contra Costa County have been diagnosed with West Nile virus. In 2006, two people died from the disease. For current human case information, please contact Contra Costa Health Services at 888-959-9911.
Contra Costa Mosquito & Vector Control District, an independent special district and public health agency, is located at 155 Mason Circle in Concord. Contact the District to report mosquito problems online or at (925) 685-9301.