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June 22, 2018 - West Nile Virus Activity Increasing In Alameda County. The presence of both West Nile virus positive dead birds and mosquitoes in Union City warrants caution.

HAYWARD, CA - To date, Alameda County Mosquito Abatement District has detected 4 dead birds and 7 groups of mosquitoes which have tested positive for West Nile virus.  The birds were collected from Union City and Castro Valley. The mosquitoes were collected in Union City and Hayward.  Recent West Nile virus positive detections indicate heightened virus transmission in the Union City area west of Interstate 880.

Intensified efforts are focused on locating areas of standing water where the West Nile virus positive bird and mosquito were discovered. Residents are urged to be proactive by eliminating sources of water where mosquitoes can breed and protecting themselves from mosquito bites. If you come across a dead bird please report it by calling (877)WNV-BIRD or online at


"Infected mosquitoes in the area means there is an increased risk for West Nile virus transmission to people," says Laboratory Director Eric Haas-Stapleton.  "Protect yourself and your family by applying mosquito repellent when spending time outdoors.  Containers of water in yards should be dumped and drained, or tightly covered to prevent mosquitoes from breeding in your neighborhood."


Mosquitoes may breed in almost any type of standing water 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.

As of June 22nd, California has had 27 dead birds, over 30 mosquito samples, and 9 humans test positive for West Nile virus.  

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, limit outdoor activities during this time.
  • DEFEND yourself from mosquito bites by wearing long pants and long-sleeved shirts and apply insect repellent containing EPA-registered active ingredients such as DEET, Picaridin, IR3535, or 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, West Nile virus, or to request any of the District services visit or call (510) 783-7744. Residents can also request mosquitofish for their fish ponds, horse troughs, or neglected swimming pools at the the District office located in Hayward at 23187 Connecticut St.  For information concerning West Nile virus symptoms, prevention or testing please contact the Alameda County Public Health Department at (510) 267-8001.