CONCORD, CALIFORNIA - The Contra Costa Mosquito & Vector Control District (District) reports a second group of mosquitoes has tested positive for West Nile virus (WNV) in Contra Costa County.

The latest group of mosquitoes were collected from traps in an area east of Brentwood. This is the second group of mosquitoes to test positive for WNV so far this year in Contra Costa County. The first group of mosquitoes to test positive was also from an area in eastern Contra Costa County.

It only takes one bite from an infected mosquito to transmit WNV to a person. And the mosquitoes that can transmit WNV can fly up to 15 miles, putting citizens at risk far from where the mosquitoes became infected. To reduce the risk of WNV, the District recommends that all Contra Costa County residents take steps to reduce the risk of the leading cause of mosquito-borne disease in the United States.

"Dumping out standing water and wearing repellent are two important things county residents can do to reduce the risk of WNV. Dumping out standing water denies mosquitoes a place to develop from egg to biting adult and wearing repellent can repel mosquitoes and reduce the risk of a person being bitten by an infected mosquito," said Steve Schutz, Ph.D., Scientific Program Manager.

In addition to dumping out standing water, the District advises residents should use repellents containing specific ingredients as well as other ways to reduce the risk of WNV.

  • Use repellents containing DEET, Picaridin, or Oil of Lemon Eucalyptus.
  • Keep swimming pools chlorinated and filtered because just one neglected pool can produce up to 1 million mosquitoes and affect people up to 15 miles away.
  • Avoid the outdoors when mosquitoes are present, typically dawn and dusk.

Contra Costa County residents can also report dead birds by phone at (877) WNV-BIRD (968-2473) or online.

Since 2005, 73 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.