Contra Costa Mosquito & Vector Control

FOR IMMEDIATE RELEASE     -     October 18, 2013

Contact: Deborah Bass
              Public Affairs Mgr.

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

For human cases, please contact Contra Costa Health Services at 888-959-9911


People likely infected in September


CONCORD, CALIFORNIA - - The Contra Costa Mosquito & Vector Control District (District) has been informed that two more people from Contra Costa County have tested positive for West Nile virus. Both are from the eastern portion of the county. The two adults were infected by virus-carrying mosquitoes most likely in late September.


The District also reports a dead bird from Alamo has tested positive for the virus. The bird was found near Golden Grass Drive and Stone Valley Road.


"This year we have received five reports of people who have tested positive for West Nile virus. Through patient interviews, it is likely only two were infected locally. The other three people were determined to have been infected outside of Contra Costa County," said Deborah Bass, spokeswoman for the District. "It's very important to remember that the majority of West Nile virus cases are not reported. In fact, based on data from the CDC, we estimate that in Contra Costa County up to 280 people were affected by the virus last year, they just didn't know it or it wasn't reported."


Birds are the reservoir for West Nile virus. The two species of mosquitoes in Contra Costa County capable of transmitting the virus prefer to feed on birds; however, people can become infected when a mosquito bites an infected bird and then a person. 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. West Nile virus of the severe form can be fatal.   


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

  • 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. 

Since 2005, 49 people in Contra Costa County have been diagnosed with West Nile virus. In 2006, two people died from the disease. Recent studies have shown that the majority of cases are not diagnosed and grossly under reported. For 2013, a total of  five people (three residents report exposure out of area) , 13 groups of mosquitoes, 68 dead birds and seven chickens have tested positive for the virus.  


Visit the District's website or click on these links for  current West Nile virus activity  or to  receive automatic emails for when the District fogs for adult mosquitoes.


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.    

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