Los Angeles may be best known for its blue skies, beaches and movie premieres, but in recent years it has held another unenviable distinction: the most mosquito-infested city in America.
And this year has been particularly nightmarish, thanks to a series of heat waves and a powerful El Niño. Locals have called it a “hell” summer as clouds of mosquitoes invade backyards and leave diners on outdoor patios scratching their ankles.
This double whammy of heat and humidity makes 2026 one of the worst mosquito years in recent history, causing a surge in West Nile virus cases and raising fears that these pests could spread other diseases, including dengue, introduced by travelers. With humidity forecast this week and nighttime temperatures likely to stay above 50F (10C), there appears to be no end in sight for a problem that local officials have struggled to contain over the past decade.
“I’ve been here my whole life and the amount of mosquitoes I’ve seen this summer is insane,” one TikTok user said in a video with more than 20,000 likes. “Everyone’s talking about it… You can’t even go in your yard. You can’t even sit in your car with the windows down. They’re infested everywhere.”
Southern California residents have struggled all year to keep winged leeches at bay. Some have had to sleep in long sleeves after failing to kill the mosquitoes colonizing their homes. Others tried to seal the cracks under their doors with towels.
“It’s an absolute nightmare,” El Seguno resident Truman Hedding told Fox 11 News earlier this year. “We invest a lot of money to live in a beautiful city like El Segundo. The last thing we want is to stay up all night fighting mosquitoes.”
“A busy season”
Los Angeles County has recorded more than 180 cases of West Nile virus this year, according to the county public health department — the highest number in nearly a decade. And mosquito season is still far from over.
“This year in particular, in our area, mosquito activity and disease activity have been higher,” said Anais Medina Diaz, communications director for the San Gabriel Mosquito and Vector Control District. “We can attribute that to some connection with the environment and how warm it has been this year – particularly because we had a very warm winter.
Mosquito activity drops when temperatures approach 50F at night. But this winter has been exceptionally mild, with heatwaves in February and March keeping mosquitoes active. The unusually wet and humid summer made their reproduction easier.
The region has been gripped by a record heatwave since early October, although forecasts point to relief underway. But temperatures won’t drop enough in most places to completely stop mosquito activity, while upcoming rains will give them new places to breed.
Southern California hasn’t always been a hotbed for mosquitoes. The most widespread endemic mosquito in the region, the Culex quinquefasciatus – often referred to by the easier-to-pronounce name “quinx” – prefers to target birds rather than humans. This preference exposes the quinx to West Nile virus after biting birds, such as crows, known to harbor the disease. The infected quinx can then transmit the disease to humans when bitten.
The Orange County Mosquito and Vector Control District monitors disease threats using a wide array of traps located throughout the region. So far, some 850 of them have tested positive for West Nile virus, according to the control district’s public information officer, Brian Brannon.
“That doesn’t mean 850 mosquitoes – that means 850 traps filled with mosquitoes carrying West Nile virus,” Brannon said. “We’ve had a pretty busy season.”
However, the mosquitoes that Southern Californians are most likely to notice are those of the Aedes genus, which first appeared in the area in 2014 and have proliferated since. Known locally as “ankle biters,” Aedes mosquitoes target humans. Because the mosquito is new to the area and people have had less exposure to it, Aedes bites may leave larger marks, according to Medina Diaz.
“They like human blood,” she said. “They will bite you several times to get a complete blood meal.”
Aedes are not associated with West Nile virus, but they are known to spread diseases such as dengue, chikungunya, Zika and yellow fever.
This year’s humidity has particularly helped the invasive Aedes species thrive this year. Aedes mosquitoes can breed in puddles as small as a tablespoon.
Biting back
Although nowhere in Southern California is truly safe from mosquitoes, the invasive Aedes species is more common in suburban neighborhoods and valleys, where people’s habits tend to create many small puddles, like saucers under potted plants or unattended water bowls for pets.
One of the most effective ways to combat mosquitoes, and by far the cheapest, is to eliminate standing puddles. Local authorities spend a lot of time on this, but mistrust among landowners can make it difficult to do thorough work.
“Not everyone wants us on their property, so that creates a real barrier,” said Angela Caranci, science and engineering manager for the Los Angeles County Vector Control District. “Half the battle is convincing people that we’re not trying to sell them a subscription pest control service.”
For major problem areas, vector control districts also spray adulticide, an insecticide that targets adult mosquitoes, diluted to a concentration of about two tablespoons per acre. According to Brannon, proactive spraying is one of the reasons West Nile cases have not exceeded 2014 numbers, despite such a mosquito-infested year.
“It doesn’t take much, but what we want to do is take down the adults who are flying with West Nile,” he said. said.
One of the most promising techniques deployed in recent years involves sterilizing males using X-rays and then releasing them in targeted areas. Only female mosquitoes bite humans and use their blood to feed their eggs. With enough sterile males in the environment, local authorities pushed back targeted mosquito populations by more than 80% at some experimental sites. This is a strategy long used in agriculture to control harmful insects that feed on valuable crops.
But while promising, flooding the area with sterile males remains a limited tool. This works best on Aedes mosquitoes, which have a small home range and whose annihilation poses few ethical problems because they are a non-native invasive species.
But while at least three species of Aedes mosquitoes live in Southern California, local officials only have the capacity to target the largest and best-studied: Aedes aegypti. It’s also very expensive. An experimental program in the San Gabriel Valley cost about $30,000 to cover just 25 acres (10 hectares), Medina Diaz said. Despite its success, homeowners — particularly businesses — have been reluctant to vote to raise their taxes to foot the bill for mosquito abatement, according to the Los Angeles Times.
Take your zapper
For now, Southern California has no choice but to start getting used to the idea that mosquitoes are likely to become a more important part of local life. The best ways to avoid bites, other than avoiding the outdoors altogether, are to cover your skin with long sleeves and pant legs, and to use a repellent containing one of four ingredients known to actually work: Deet, picaridin, IR3535, or lemon eucalyptus oil.
“Most of our residents are used to not having mosquitoes, and that has now changed,” Medina Diaz said. “If you want to avoid mosquito bites, you will need to make wearing a repellent part of your routine.”
Because they can breed in very small bodies of water, Aedes mosquitoes have a knack for sneaking into homes, where they can be difficult to eliminate.
The first step in eliminating them is to remove all standing water, including saucers under the plants. To combat persisters, Brannon suggests purchasing an electric fly swatter.
“It looks like a tennis racket, and when you hit them, it zaps them,” he said. “It’s a very rewarding activity. It makes me smile.”
Gn Health
