Los Angeles mosquitoes have become an unwelcome hallmark of recent summers, with the city repeatedly ranked the most mosquito-infested in the United States. This year has been especially difficult as prolonged heatwaves and a strong El Niño amplified swarms across Southern California, leaving residents dreading evenings outdoors and even quick errands with the car windows down.
Relentless heat combined with higher humidity has pushed 2026 into one of the worst mosquito years in recent memory, contributing to a rise in West Nile virus cases and fueling fears that travelers could seed other illnesses such as dengue. With more moisture in the forecast and overnight temperatures expected to remain above 50F, officials say conditions favor continued activity.
Residents across the region describe a near-constant battle. Some have taken to sleeping in long sleeves or blocking door gaps with towels to keep insects out. “It’s an absolute nightmare,” said Truman Hedding of El Segundo, adding that late-night mosquito fights have become routine.
‘A busy season’ for Los Angeles mosquitoes
Los Angeles County has recorded more than 180 West Nile virus cases this year, according to the county public health department, the highest tally in nearly a decade with weeks of mosquito season still to go.
“This year in particular for our area has been higher mosquito activity and higher disease activity,” said Anais Medina Diaz, communications director for the San Gabriel Valley Mosquito and Vector Control District, citing an unusually warm winter that allowed mosquitoes to stay active and a moist, humid summer that accelerated breeding.
Typically, mosquito activity drops as overnight lows near 50F. Instead, this winter delivered unseasonable warmth, including February and March heatwaves, followed by a record-breaking hot spell in early October. Forecasts suggest some relief, but not enough to shut down mosquito activity, and upcoming rains could create new breeding sites.
Southern California’s endemic Culex quinquefasciatus, often called “quinx,” primarily targets birds, which can expose it to West Nile virus. Infected quinx can then pass the virus to humans. Orange County’s vector control network has detected West Nile-positive mosquitoes in roughly 850 traps this year, according to public information officer Brian Brannon. “That doesn’t mean 850 mosquitoes. That means 850 traps full of mosquitoes with West Nile virus,” he said. “We’ve had a pretty busy season.”
What most residents notice, however, are the invasive Aedes species that arrived in 2014 and have since spread widely. Nicknamed “ankle biters,” Aedes prefer humans and can bite repeatedly. Medina Diaz noted their bites can leave larger welts because people here have had less exposure to them.
While Aedes are not tied to West Nile virus, they can transmit dengue, chikungunya, Zika and yellow fever. This year’s abundant moisture has given Aedes an extra boost, as they can reproduce in as little as a tablespoon of standing water.
Biting back
Nowhere in Southern California is free from mosquitoes, but Aedes thrive in suburban neighborhoods and valleys where everyday habits create bite-sized breeding spots, from plant saucers to neglected pet water bowls. Officials say the most effective and affordable defense is eliminating stagnant water, though property access remains a barrier. “Not everyone wants us on their property, so it creates quite a hurdle,” said Angela Caranci, a scientific-technical manager with the Greater Los Angeles County Vector Control District.
For hot spots, districts deploy ultra-low-volume sprays of adulticide, diluted to about two tablespoons per acre, to knock down flying adults and limit virus transmission. Brannon said proactive spraying is one reason West Nile numbers have not surpassed 2014 levels despite the intense season.
Agencies are also piloting the release of sterilized male mosquitoes, produced with X-rays, to suppress local populations. Since only females bite, flooding areas with sterile males can reduce Aedes numbers by more than 80 percent in test sites. The approach works best on Aedes, which have smaller home ranges and are non-native. But capacity is limited to Aedes aegypti, and costs are steep. Medina Diaz said a San Gabriel Valley trial cost about $30,000 to cover 25 acres, and efforts to fund broader work have faced resistance from property owners wary of higher assessments.
Grab your zapper
With warmer, wetter conditions extending mosquito activity, officials urge residents to adjust. The most reliable repellents contain DEET, picaridin, IR3535, or oil of lemon eucalyptus, and long sleeves and pants offer added protection. Indoors, removing every source of standing water is critical since Aedes can breed in tiny pools. For stragglers, Brannon recommends an electric fly swatter. “It looks like a tennis racket, and when you hit them, it zaps them,” he said. “It’s a very fulfilling activity.”
As Los Angeles mosquitoes continue to thrive in the lingering heat, officials say vigilance at home, paired with targeted public health interventions, will be key to curbing bites and limiting disease this season.
Relentless heat combined with higher humidity has pushed 2026 into one of the worst mosquito years in recent memory, contributing to a rise in West Nile virus cases and fueling fears that travelers could seed other illnesses such as dengue. With more moisture in the forecast and overnight temperatures expected to remain above 50F, officials say conditions favor continued activity.
Residents across the region describe a near-constant battle. Some have taken to sleeping in long sleeves or blocking door gaps with towels to keep insects out. “It’s an absolute nightmare,” said Truman Hedding of El Segundo, adding that late-night mosquito fights have become routine.
‘A busy season’
Los Angeles County has recorded more than 180 West Nile virus cases this year, according to the county public health department, the highest tally in nearly a decade with weeks of mosquito season still to go.
“This year in particular for our area has been higher mosquito activity and higher disease activity,” said Anais Medina Diaz, communications director for the San Gabriel Valley Mosquito and Vector Control District, citing an unusually warm winter that allowed mosquitoes to stay active and a moist, humid summer that accelerated breeding.
Typically, mosquito activity drops as overnight lows near 50F. Instead, this winter delivered unseasonable warmth, including February and March heatwaves, followed by a record-breaking hot spell in early October. Forecasts suggest some relief, but not enough to shut down mosquito activity, and upcoming rains could create new breeding sites.
Southern California’s endemic Culex quinquefasciatus, often called “quinx,” primarily targets birds, which can expose it to West Nile virus. Infected quinx can then pass the virus to humans. Orange County’s vector control network has detected West Nile-positive mosquitoes in roughly 850 traps this year, according to public information officer Brian Brannon. “That doesn’t mean 850 mosquitoes. That means 850 traps full of mosquitoes with West Nile virus,” he said. “We’ve had a pretty busy season.”
What most residents notice, however, are the invasive Aedes species that arrived in 2014 and have since spread widely. Nicknamed “ankle biters,” Aedes prefer humans and can bite repeatedly. Medina Diaz noted their bites can leave larger welts because people here have had less exposure to them.
While Aedes are not tied to West Nile virus, they can transmit dengue, chikungunya, Zika and yellow fever. This year’s abundant moisture has given Aedes an extra boost, as they can reproduce in as little as a tablespoon of standing water.
Biting back
Nowhere in Southern California is free from mosquitoes, but Aedes thrive in suburban neighborhoods and valleys where everyday habits create bite-sized breeding spots, from plant saucers to neglected pet water bowls. Officials say the most effective and affordable defense is eliminating stagnant water, though property access remains a barrier. “Not everyone wants us on their property, so it creates quite a hurdle,” said Angela Caranci, a scientific-technical manager with the Greater Los Angeles County Vector Control District.
For hot spots, districts deploy ultra-low-volume sprays of adulticide, diluted to about two tablespoons per acre, to knock down flying adults and limit virus transmission. Brannon said proactive spraying is one reason West Nile numbers have not surpassed 2014 levels despite the intense season.
Agencies are also piloting the release of sterilized male mosquitoes, produced with X-rays, to suppress local populations. Since only females bite, flooding areas with sterile males can reduce Aedes numbers by more than 80 percent in test sites. The approach works best on Aedes, which have smaller home ranges and are non-native. But capacity is limited to Aedes aegypti, and costs are steep. Medina Diaz said a San Gabriel Valley trial cost about $30,000 to cover 25 acres, and efforts to fund broader work have faced resistance from property owners wary of higher assessments.
Grab your zapper
With warmer, wetter conditions extending mosquito activity, officials urge residents to adjust. The most reliable repellents contain DEET, picaridin, IR3535, or oil of lemon eucalyptus, and long sleeves and pants offer added protection. Indoors, removing every source of standing water is critical since Aedes can breed in tiny pools. For stragglers, Brannon recommends an electric fly swatter. “It looks like a tennis racket, and when you hit them, it zaps them,” he said. “It’s a very fulfilling activity.”
As Los Angeles mosquitoes continue to thrive in the lingering heat, officials say vigilance at home, paired with targeted public health interventions, will be key to curbing bites and limiting disease this season.
