One locally acquired dengue case was confirmed in Winter Springs, involving a person who works in the area and reported mosquito bites near the workplace.
Recent rain has boosted mosquito breeding, pushing Seminole County to intensify monitoring, fogging and larvicide treatment while urging residents to use DEET and remove standing water.
More than 32,000 acres were fogged last month, and the county said it is also using mosquito traps and sentinel chickens to watch for viruses.
The case adds to a wider Central Florida uptick: Orange County has reported five local cases and Brevard County confirmed its first last week.
Officials said dengue spreads through infected mosquito bites, not person-to-person, and warned Seminole could still see additional cases as two more are being tested.