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February 1, 2023 - First West Nile Positive Mosquito Found In 2023

First indicator of the virus circulating in Alameda County

 HAYWARD, CA - The Alameda County Mosquito Abatement District is reporting a mosquito that tested positive for West Nile virus. This is the County's first indication of West Nile virus this year.  The mosquito was collected from western Union City and tested at the District laboratory on January 31, 2023.

The District is increasing mosquito monitoring and larval control efforts throughout the area where the West Nile virus positive mosquito was discovered. 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.

"This is an unusually early start to the West Nile virus season in Alameda County" says General Manager Ryan Clausnitzer. "Given the large amount of rain we had at the end of 2022 and the beginning of this year, there are more opportunities for mosquitoes to lay their eggs and reproduce rapidly. We need the public to help by reducing mosquito breeding sites. Dump and drain or tightly cover containers that have standing water to reduce mosquitoes around your house and workplace."

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

* DUMP/DRAIN standing water on your property, since mosquitoes need water to develop.

* DAWN/DUSK is when mosquito activity peaks, so 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. 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. There is no cure for West Nile virus.  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 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.