California sees fastest West Nile spread in 20 years, urges mosquito precautions

Health officials in Southern California have reported the earliest and most rapid West Nile virus activity in two decades. In Los Angeles County, positive mosquito samples have risen to 38 this season, far above the five‑year average of four, while Orange County has detected the virus in 10 cities, including Newport Beach and Fullerton. Nationwide there are at least 48 human cases, with a single neuroinvasive case confirmed in Long Beach, California.

Officials are urging residents to protect themselves by removing standing water, using EPA‑registered repellents, wearing long sleeves and pants during dawn and dusk, and ensuring window and door screens are intact. The San Bernardino County Vector Control Program also offers courtesy inspections and mosquito‑fish for water features.

In neighboring Contra Costa County, vector officials have begun releasing Wolbachia‑treated male Aedes aegypti mosquitoes to curb populations of the species that can transmit dengue, Zika and yellow fever. The strategy aims to produce infertile eggs and reduce mosquito numbers without affecting humans or pets.