Orange County vector control warns Costa Mesa to prepare for increased mosquito activity and dengue risk in 2025
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Summary
The Orange County Mosquito and Vector Control District updated the City Council on 2024 local activity, wetland management at Fairview Park, and a pilot sterile insect technique; staff urged residents to reduce standing water and sign up for outreach.
Laura Young, general manager of the Orange County Mosquito and Vector Control District, told the Costa Mesa City Council on Jan. 21 that the district saw low West Nile activity in 2024 but expects more mosquito and disease activity in 2025.
“Last year was a very mild West Nile virus year,” Young said, adding that Costa Mesa had no positive mosquito pools and no human West Nile cases in 2024. She noted there was one West Nile human case in the county (Huntington Beach) and that California saw repeated local dengue transmission in 2024 in neighboring counties. “For dengue, it’s not a question of when we will get local transmission. It’s not a question of if we will get it. It’s when,” Young said.
The district provided a short local summary of work in Costa Mesa: 82 resident calls in 2024, 166 inspections of out-of-service pools, routine treatment of roughly 30 acres of flood channels and regular treatments of underground systems (manholes) during the breeding season. At Fairview Park Wetlands the district said a vector management plan implemented in late 2023 and continued through 2024 reduced mosquito hatch-offs dramatically, from thousands in 2022 to about 40 on average in 2024—a change Young credited to vegetation management and improved access for treatments.
District representative Bill Turpin introduced Young and reminded council members that the district is an independent special district governed by the Health and Safety Code and maintains a 35-member board with one representative from each city.
Young described the district’s toolbox—source reduction, biological control (mosquito fish), larvicides and adulticides—and discussed an ongoing sterile insect technique (SIT) pilot in Mission Viejo that irradiates male Aedes aegypti to reduce urban mosquito populations. She said the expected drivers for increased 2025 mosquito activity include drought-driven landscape watering and increased travel by visitors, which both increase breeding sources and the chance of pathogen introduction.
Council members asked about county parks and notification protocols, and Young said the district notifies the city before activities and posts on social media; she said residents can sign up for the district’s mailing list even when activity is in a county park adjacent to Costa Mesa. Council members also asked about compost/green-waste programs, and Young said Orange County has not seen a local increase in rat activity tied to green-waste collection pilot programs but that jurisdictions with less education and different storage practices reported increases.
The district encouraged the city to promote resident outreach—checking yards, removing standing water, attending community events—and invited staff to include the district in Earth Day and “concert in the park” outreach.
Ending: Council members thanked the district for the update. City and district staff said they will continue coordination on Fairview Park access and resident education ahead of the 2025 season.
