Los Angeles battles worst mosquito infestation in years amid record heat and humidity

The Infestation

Los Angeles is facing one of its worst mosquito seasons in recent history, driven by a series of heatwaves and a powerful El Niño. Residents report a summer of heavy swarms in backyards and outdoor patios. The double hit of heat and humidity has pushed West Nile virus cases to a decade high, with Los Angeles county documenting more than 180 cases this year.

Causes And Disease Spread

An unusually mild winter with heatwaves in February and March allowed mosquitoes to stay active earlier than usual. The native Culex quinquefasciatus mosquito spreads West Nile virus after biting infected birds like crows. Meanwhile, invasive Aedes mosquitoes, first appearing in 2014, target humans and can spread diseases like dengue and chikungunya. Orange County has recorded about 850 traps testing positive for West Nile virus, according to public information officer Brian Brannon.

Control Efforts

Vector control districts spray adulticide at a concentration of about two tablespoons per acre to knock down adult mosquitoes. Officials also use an experimental technique of releasing X-ray sterilized males, which has reduced targeted populations by over 80 percent in some test sites. However, this method remains costly, with a San Gabriel Valley trial costing about $30,000 for just 25 acres.

Context

Los Angeles was not always a major mosquito hotspot, but invasive species have adapted well to suburban neighborhoods and backyard water pools. Public health officials stress that residents can help curb the population by eliminating tiny pools of stagnant water in plant saucers and pet bowls.