Environment & Climate

California district releases thousands of non-biting mosquitoes to curb disease spread

The San Gabriel Valley district is releasing bacteria-infected male mosquitoes to suppress wild populations, according to The Guardian.

Updated Sep 17, 2026 · 16:37 UTC1 reports

The short version

The San Gabriel Valley mosquito control district plans to release approximately 30,000 non-biting male mosquitoes weekly, totaling nearly 500,000 insects.[The Guardian]
The released males carry Wolbachia bacteria, causing wild female mosquitoes that mate with them to lay unhatchable eggs.[The Guardian]
The strategy aims to suppress disease vectors following California's first locally acquired dengue cases reported in 2023.[The Guardian]
Program success depends on monitoring wild female populations, with past trials showing population reductions between 80% and 95% depending on local conditions.[The Guardian]

The San Gabriel Valley mosquito and vector control district plans to release nearly 500,000 male mosquitoes, at a rate of roughly 30,000 per week.[The Guardian]
The released male mosquitoes carry Wolbachia bacteria, which prevents eggs from hatching when they mate with wild females.[The Guardian]
Male mosquitoes do not bite humans.[The Guardian]
California recorded its first locally acquired dengue fever cases in Pasadena and Long Beach in 2023, followed by 14 locally acquired cases identified by the CDC between August and November 2024.[The Guardian]
Climate Central found that nearly 95% of analyzed U.S. cities have experienced an average increase of 18 days per year with temperatures suitable for disease-spreading mosquitoes compared to the early 1970s.[The Guardian]

The exact level of population reduction in the local release area remains uncertain, as past trial results have ranged from 80% to 95% depending on specific local conditions.[The Guardian]

Outlet counts describe coverage, not independent confirmation. Reports may share a wire service or original source.