June 25 brought Tulare County’s first West Nile detections of 2026, with two positive mosquito samples in Dinuba and one collected north of Visalia, the Delta Mosquito & Vector Control District said.
Lower overnight temperatures in the valley likely slowed mosquito development and population growth, while spring treatments of unmaintained pools may also have delayed the season’s start.
Late July and August still mark Tulare County’s peak West Nile period, and officials said how severe it gets will depend partly on residents removing standing water as early treatments wear off.
Nationally, the CDC said 2026 has seen the earliest U.S. West Nile season and the most human cases reported by this point in the year since 2004, contrasting with Tulare County’s slower start.