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July 29 2015 – Mosquitoes Infected With West Nile Virus Confirmed in Alameda County

First mosquitoes positive for West Nile virus in Alameda County for 2015

HAYWARD, CALIFORNIA – The Alameda County Mosquito Abatement District has received confirmation from the State of two West Nile virus positive groups of mosquitoes.  Both groups of mosquitoes were collected from the northern part of Fremont on the night of July 22, 2015.  In addition, there have been five West Nile virus positive birds found in Fremont this year.

The District has greatly increased surveillance and larval control efforts throughout the areas with positive West Nile virus detections.  Every effort is being made to locate areas of standing water where mosquitoes may breed including but not limited to catchbasins, stormdrain systems, and swimming pools.  Neglected swimming pools continue to be a mosquito breeding issue in Alameda County.  If you or anyone you know has an unmaintained swimming pool please inform the District so the proper treatment can be made.

“A single neglected swimming pool can produce thousands of mosquitoes capable of spreading West Nile virus,” says District Manager Ryan Clausnitzer.  “We can provide free mosquitofish or treatments to prevent mosquito breeding.”

As of July 27th, California has had 247 dead birds, 756 mosquito samples, 43 sentinel chickens, and 1 human test positive for West Nile virus.  The human case did result in a fatality and the positive number of both mosquitoes and sentinel chickens is higher than this time last year.

Reduce the risk of contracting mosquito-borne diseases by following these guidelines:

  • DUMP/DRAIN standing water on your property because that is where mosquitoes develop.
  • DAWN/DUSK is when mosquito activity peaks, so limit outdoor activities during this time.
  • DEFEND yourself when mosquitoes are biting by wearing long pants and long-sleeved shirts and apply insect repellent containing EPA-registered active ingredients such as DEET, Picaridin, IR3535, and Oil of lemon eucalyptus.
  • DOOR/window screens should be in good repair with no tears or holes.

West Nile virus is transmitted to people and animals through the bite of an infected mosquito.  There is no cure for West Nile virus.  Approximately one in five people who are infected with West Nile virus will develop symptoms such as fever, headache, body aches, joint pains, vomiting, or rash.  Less than one percent will develop a serious neurological illness such as encephalitis or meningitis.  Adults over 50 years old and people with compromised immune systems are at increased risk of serious complications.  Anyone who develops symptoms should seek medical care immediately.

Horses are very susceptible to West Nile virus and vaccines are available.  Horse owners are advised to contact their veterinarians regarding timely vaccinations.

For information about mosquitoes and West Nile virus visit  Residents can request mosquitofish for their fish ponds, horse troughs, etc. by contacting the District office located in Hayward at 23187 Connecticut St. or by calling (510)783-7744.  For information concerning West Nile virus symptoms, prevention or testing please contact the Alameda County Public Health Department at (510)267-8001.