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June 1, 2023 - Dead Birds Infected With West Nile Virus Confirmed In Alameda County

HAYWARD, CA - The Alameda County Mosquito Abatement District is reporting that two dead birds tested positive for West Nile virus on May 31, 2023. While the district found a group of West Nile positive mosquitoes at the beginning of the year in January, this is the County's first indication of active virus transmission in 2023. The dead bird was collected from Pleasanton, CA and tested at the District laboratory on May 31, 2023. Dead birds play an important role in the District's ability to monitor West Nile virus activity in Alameda County. Public reporting of dead birds is critical to our surveillance program.

The District is increasing mosquito monitoring and larval control efforts throughout the area where the positive West Nile virus dead birds were 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. Anything that can hold water for more than 4 days such as buckets, tires, and fountains can produce mosquitoes.

“As the entire region has noticed, we have had far more rain this year than we have had for many years,” notes General Manager Ryan Clausnitzer, “and excess standing water creates more opportunities for mosquitoes to produce.” The district reminds residents that the best way to prevent mosquitoes from producing is to find areas with standing water on their property and to remove it. “This local virus positive detection by our Laboratory Staff reminds the public West Nile virus is endemic in our community and the best way to stop any future transmission is by decreasing the numbers of mosquitoes.”

As of May 26, 2023 California Public Health has reported 10 West Nile positive dead birds and 3 positive mosquito samples. No human cases have been reported so far in 2023. 

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. For information concerning West Nile virus symptoms, prevention or testing please contact the Alameda County Public Health Department at (510) 267-8001.