Huntington Beach has recorded two human infections of West Nile virus amid an unusually intense Mosquito and vector season across Orange County, health and vector-control officials say. Countywide, agencies have identified 747 positive mosquito samples and 18 human cases so far this season — a sharp rise from last year.
Early, intense season strains local surveillance
Officials with the Orange County Mosquito and Vector Control District (OCMVCD) warned this summer that early detections of infected mosquitoes signaled an active season. The agency’s recent mapping of positive mosquito samples and human infections shows the virus is present across multiple cities, with Huntington Beach and Costa Mesa among the localities reporting human cases.
OCMVCD spokesman Brian Brannon told reporters the current season is “definitely one of the worst years we’ve seen,” noting that West Nile infections are often undercounted because many people only seek care when symptoms become severe. He said the agency has been responding by targeting known hotspots with larvicides and adulticides to interrupt mosquito breeding and reduce adult populations.
Control measures underway in affected neighborhoods
Vector-control crews are using two primary tactics in areas showing high mosquito activity:
- Larvicide (BTI): Bacillus thuringiensis israelensis is applied to standing water to kill mosquito larvae before they mature.
- Ultra-low-volume adulticide treatments: Truck-mounted equipment sprays after midnight to reduce adult mosquito numbers in residential neighborhoods.
Brannon said the BTI product used by the district is commercially available and is considered safe for humans, pets and pollinators. He also cautioned that identifying the precise locations and timing of human infections is often limited by patient privacy protections; county health officials declined to comment on specifics of individual cases.
Numbers show sharp year-over-year increase
Public records and agency statements show the scale of the uptick. The OCMVCD had identified 747 positive mosquito samples as of the latest report — more than four times the 186 positive samples detected during all of 2025. Human cases are likewise rising; the county has reported 18 people with West Nile virus this season compared with four infections recorded last year.
| Metric | 2026 (season-to-date) | 2025 (all year) |
|---|---|---|
| Positive mosquito samples | 747 | 186 |
| Human West Nile cases | 18 | 4 |
Public health and vector-control authorities point to weather patterns as a contributing factor. The ongoing El Niño is producing warm, humid conditions and surf patterns that can create more breeding habitat for mosquitoes, officials say, potentially prolonging and intensifying transmission risk.
“With West Nile virus, people typically only report it when they get really sick. So if we have 18 people who’ve come forward, there are certainly more out there,” OCMVCD spokesman Brian Brannon said.
What residents should know
While county agencies continue surveillance and treatment, public-health guidance stresses individual precautions. The district is focusing treatments in neighborhoods with demonstrated mosquito activity and will continue residential spraying programs after midnight where needed. Residents with health concerns or questions about mosquito activity in their area are advised to consult county resources and their health providers.
As the season progresses, Huntington Beach officials and regional health partners are monitoring case counts and vector data closely. For now, the combination of elevated mosquito infection rates, rising human cases and weather conditions associated with El Niño suggests local residents should remain vigilant about mosquito avoidance and report standing water or heavy mosquito activity to vector-control authorities.
