CONCORD, CALIFORNIA - The Contra Costa Mosquito & Vector Control District (District) reports a group of mosquitoes has tested positive for West Nile virus (WNV) in Contra Costa County. The mosquitoes were collected from a trap in the city of Oakley. This is the first group of mosquitoes to test positive for WNV so far this year in Contra Costa County.

Certain species of birds may carry WNV. Once a mosquito bites an infected bird, the mosquito can become infected with the ability to transmit WNV to another animal or a person through a single mosquito bite.

WNV can grow more efficiently when temperatures are consistently warmer than 55 degrees. The District advises County residents to take action to reduce the risk of WNV by avoiding mosquito bites.

"It is important that Contra Costa County residents take precautions to avoid mosquito bites by using an effective insect repellent when outdoors, especially at dawn and dusk. Wear long-sleeved shirts and pants to reduce the amount of exposed skin that can be bitten. And, if possible, avoid being outdoors where mosquitoes are present," said Steve Schutz, Ph.D., Scientific Program Manager.

Another way to reduce the risk of mosquitoes is to dump out any amount of standing water. Mosquitoes develop from egg to biting adult in water. Even the small amount of water that can collect in a bottle cap can produce mosquitoes. Also, make sure window and door screens do not have any rips or tears and that screens fit properly.

According to the Centers for Disease Control and Prevention (CDC) when used as directed, Environmental Protection Agency (EPA)-registered insect repellents are proven safe and effective. The District recommends using EPA-registered insect repellents with one of the following active ingredients:
  • DEET
  • Picaridin
  • Oil of Lemon Eucalyptus.

Always follow the instructions on the label when using an insect repellent.

Contra Costa County residents can report dead birds by phone at (877) WNV-BIRD (968-2473) or online. County residents can also request mosquito service for residential property by calling (925) 685-9301 or online.

Since 2005, 75 people in Contra Costa County have been diagnosed with West Nile virus. In 2006, two people died from the disease. For human case information, please visit the California Department of Public Health Vector-Borne Disease Section online.
 
Contra Costa Mosquito & Vector Control District, an independent special district and public health agency, is located at 155 Mason Circle in Concord.