CONCORD, CALIFORNIA - The Contra Costa Mosquito & Vector Control District (District) reports a dead bird and a group of mosquitoes have tested positive for West Nile virus (WNV) in Contra Costa County. The dead bird was picked up in Martinez and the mosquitoes were collected from traps in an agricultural area east of Knightsen. This is the first bird and second group of mosquitoes to test positive for WNV so far this year 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 WNV to another bird or a person through a mosquito bite.

The discovery of one dead bird and infected mosquitoes in the middle of a heatwave, is an important reminder that hot weather can increase the risk of WNV transmission, according to the District's Scientific Program Manager Steve Schutz, Ph.D.

"Mosquitoes develop from egg to adult more quickly in warmer weather and West Nile virus also replicates faster and reaches high levels within the mosquitoes when temperatures stay above 54 degrees overnight, so hot weather significantly increases the chances of disease transmission to people," said Schutz.

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

County residents can also report dead birds 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.