Skip to main content

First West Nile positive mosquito for 2024 found in Alameda County

A mosquito on skin with text about West Nile virus.

HAYWARD,CA March 13, 2024

 The Alameda County Mosquito Abatement District found a West Nile positive mosquito, a first for this year. This is the County's first West Nile virus positive mosquito, after finding the two West Nile virus birds in Union City earlier this year. The mosquito was collected from western Union City and tested at the District laboratory on March 8th, 2024.

The District is increasing mosquito monitoring and larval control efforts throughout the area where the West Nile virus positive mosquito was discovered. Residents may see our trucks and labelled mosquito traps in the areas near 880 and Alvarado Niles Rd. You can find the map of West Nile positives for the year on our website: 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.

“It is unusual for us to have a West Nile virus detection this early in Alameda County, though it is not surprising after we found two West Nile positive birds in Union City recently.” says General Manager Ryan Clausnitzer. "We have had a large amount of rain in the past few months, which means more places for mosquitoes to lay their eggs and reproduce rapidly. While we are controlling the mosquitoes in public spaces, we rely on residents to reduce their risk of mosquitoes on their own property. 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.


About Alameda County Mosquito Abatement District

Alameda County Mosquito Abatement District is committed to improving the health and comfort of Alameda County residents by controlling mosquitoes and limiting the transmission of mosquito-borne diseases. Learn more about our work at

 Media Contact:

Name: Judith Pierce

Title: Public Outreach Coordinator

Phone: 510-783-7744

Email address: