West Nile virus activity spikes in Southern California, officials urge precautions
Mosquito testing in Los Angeles and Orange counties shows a sharp rise in West Nile virus-positive samples, prompting health agencies to advise residents on bite prevention.
Mosquito surveillance in Southern California has detected a marked increase in West Nile virus-positive samples this season. In Los Angeles County, the Greater Los Angeles County Vector Control District reported 38 positive mosquito pools, far above the five-year average of four at this point in the year. The first human case in California this year involved a Long Beach resident hospitalized with neuroinvasive illness.
Orange County officials confirmed the presence of virus-carrying mosquitoes in ten cities, including Newport Beach, Fullerton and Anaheim. The district has identified 38 positive mosquito pools, compared with five in 2023 and four in 2022, and described the current activity as “above-average for this time of year.”
The Centers for Disease Control and Prevention notes that, as of June 30, the United States has recorded 48 human West Nile cases, 38 of which are severe neuroinvasive infections—the highest mid-year total since 2004. While most infections are asymptomatic, about 20% develop mild flu-like symptoms and roughly 1% progress to serious brain or nervous-system involvement, which can be fatal.
Health officials recommend standard mosquito-bite prevention measures: applying repellents containing DEET, IR3535, oil of lemon eucalyptus or picaridin; wearing long sleeves and pants during dawn and dusk; eliminating standing water around homes; and maintaining window and door screens. Residents are also urged to report neglected swimming pools or large breeding sites to local vector control districts.