Contra Costa Mosquito & Vector Control

FOR IMMEDIATE RELEASE     -     October 4, 2012

Contact: Deborah Bass
              Public Affairs Mgr.

(925) 771-6112 - office
(925) 260-4670 - mobile 


October Heat Wave Stretches West Nile Virus Season into Fall


CONCORD, CALIFORNIA - - The Contra Costa Mosquito & Vector Control District announced today that five more birds and one chicken have tested positive for West Nile virus. The birds were found in Brentwood, Concord, Discovery Bay, Pleasant Hill, and Walnut Creek. The chicken is part of sentinel flock located in Oakley.


The latest birds tested positive as an early October heat wave pushed temperatures in many Contra Costa County communities near or past the century mark. The heat plays a significant role in both mosquito and virus activity.


"The mosquitoes that can transmit West Nile virus thrive in warm weather because higher temperatures allow them to complete their life cycles more quickly," said the District's Scientific Program's Manager Steve Schutz, Ph.D.  "Higher temperatures also allow the virus to grow rapidly, increasing the chances that birds or mosquitoes can become infected."


The District asks all residents to be vigilant about avoiding mosquitoes by wearing repellent when mosquitoes are present. Dump or drain any standing water to prevent mosquitoes from having a place to lay their eggs, and  report dead birds because they are often the first sign of West Nile virus in a particular location. Reporting neglected swimming pools is also very important because one neglected swimming pool can produce 1 million mosquitoes that can affect people up to five miles away. 


Since 2005, 39 people in Contra Costa County have been diagnosed with West Nile virus. In 2006, two people died from the disease. A recent study has shown that the majority of cases are undiagnosed and grossly under reported. This year, a total of two people, 19 groups of mosquitoes, 56 dead birds, and seven chickens have tested positive for the virus. The number of mosquitoes, birds and chickens have already surpassed the number of insects and animals that tested positive for the virus in all of 2011. 


For current West Nile virus activity  and to receive  emails when the District fogs for adult mosquitoes, please visit the District's website and sign up for automatic email notification



West Nile virus symptoms of the mild form include fever, headache, tiredness, body aches, and swollen lymph glands. While the illness can last only a few days, even healthy people have reported being sick for several weeks.

Less than one percent of individuals (about 1 in 150 people) infected with West Nile virus will develop severe illness. The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent. West Nile virus infection can be fatal.    


Residents are urged to help reduce their risk of contracting mosquito-borne diseases by following these guidelines: 

  • Don't produce mosquitoes on your property. Dump or drain standing water. Mosquitoes can't begin their life without water.
  • Defend yourself against mosquitoes using repellents containing DEET, Picaridin, or Oil of Lemon Eucalyptus.
  • Avoid being outdoors when mosquitoes are present, typically Dawn and Dusk.
  • Report neglected swimming pools by calling 925-771-6195 or visiting  Anonymous calls accepted. Just one neglected pool can produce more than 1 million mosquitoes and affect people up to five miles away.  
The District makes every effort to notify residents about West Nile virus activity and adult mosquito spraying events. People wishing to be notified about adult mosquito spraying in residential areas have several options. They may visit the District's website and opt to receive the maps and notifications automatically by email.There is also an option to receive media releases and the Mosquito Bytes newsletter. These communications are posted directly on the District's website. Spray schedules are also available by calling the District at (925) 771-6195 and listening to a recorded message. 

Contra Costa Mosquito & Vector Control District, an independent special district and public health agency, is located at 155 Mason Circle in Concord. Call the District to report mosquito problems at (925) 771-6195 or visit their office between 8:00 a.m. and 4:30 p.m. to get FREE mosquitofish for ornamental ponds, horse troughs or neglected swimming pools.  

For information concerning human West Nile virus symptoms, prevention, or testing, please call the Contra Costa Health Services department at (888) 959-9911. For information concerning West Nile virus and horses, please call the California Department of Food and Agriculture Animal Health Branch at (916) 654-1447. 

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