Home Brentwood West Nile Virus Risk in Contra Costa County Continues as More Birds and Sentinel Chickens Test Positive

West Nile Virus Risk in Contra Costa County Continues as More Birds and Sentinel Chickens Test Positive

by ECT

CONCORD, CA – The Contra Costa Mosquito & Vector Control District (District) has confirmed two sentinel chickens and three dead birds have tested positive for West Nile Virus (WNV). Two birds are from Brentwood, one is from Concord. This is the first bird from Concord to test positive for WNV this year. Both chickens are from Holland Tract in East Contra Costa County. These are the first sentinel chickens of the year to test positive for WNV in Contra Costa County.


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.


Chickens serve as sentinels of WNV transmission in a particular area because when an infected mosquito bites a chicken, the chicken is naturally resistant to WNV and does not get sick. Chickens do, however, develop antibodies that can be detected in lab tests and confirm when they have been exposed to WNV. Due to their antibodies, chickens are an important tool in the District’s Integrated Vector Management (IVM) approach to reducing the risk of WNV.


So far this year, a total of 11 groups of mosquitoes, 15 dead birds and now two sentinel chickens have tested positive for WNV in Contra Costa County.


While most of the WNV activity so far this year has been in East Contra Costa County, the District’s Scientific Program Director Steve Schutz, Ph.D., reminds county residents to take precautions no matter where you are within the county.


“The first positive bird of the year was from Martinez. Now, with a bird from Concord, it’s an important reminder that West Nile virus is not restricted to just one part of Contra Costa County. It is very important that all Contra Costa County residents take this virus seriously. Take precautions to reduce the risk of mosquito bites now and well into the fall because the risk of virus transmission can continue until average overnight temperatures drop below 55 degrees for a week or longer.”


Contra Costa County residents can reduce the risk of mosquito bites and WNV 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
  • Reporting dead birds to the state hotline by phone at (877) WNV-BIRD (968-2473) or online


Since 2005, 70 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.

You may also like