JUANA SUMMERS, HOST:
This fall, several people have caught dengue fever in Los Angeles County. The disease is transmitted by mosquitoes, and it can cause dangerous fever - sometimes even death. But it has been rare in most of the U.S. Now, dengue's range might be shifting, in part because of climate change. NPR's Alejandra Borunda tagged along with the team trying to halt the outbreak.
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MANNY LARA: Thank you, ma'am. Appreciate it.
ALEJANDRA BORUNDA, BYLINE: In a tidy backyard in the Los Angeles suburb of West Covina, insect control technician Manny Lara is hunting for mosquitoes.
LARA: So I'm checking these trash cans here. Yes, I see there's - there's adults here.
BORUNDA: A swarm of adult mosquitoes fly out of a trash can lid. Lara works for the local vector control agency, which tries to prevent the spread of insect-borne diseases. He's out here looking for any bits of standing water - from trash cans to house plants, or even tiny bottle caps. That's where these mosquitoes like to breed.
LARA: I think that one - that one is just emerging. Do you see that one?
BORUNDA: And he's just found a buzzing, horrifying motherlode - adult mosquitoes and hundreds of larvae in the process of hatching. These are an invasive species called Aedes aegypti. Lara says they're a lot more aggressive than California's native mosquitoes.
LARA: Sometimes they'll bite you multiple times. So they're just kind of like, you know, let me taste this person, let me taste that person, you know?
BORUNDA: That's annoying, and it's also a health problem because unlike native mosquitoes, these can transmit dengue fever. Dengue is a tropical disease. Sometimes it's called breakbone fever because it makes people's bones ache. In the worst cases, it can even kill. And travelers often get dengue abroad, but historically, you couldn't catch it in Southern California. That's changing. Last year, for the first time ever, officials reported two cases caught locally.
Aiman Halai is an epidemiologist with the Los Angeles County Department of Public Health. She says last year...
AIMAN HALAI: Was a reality check that this can happen in our area.
BORUNDA: So this year, health officials were on the lookout. So far, they've found eight cases caught here in LA County, and Halai says this is probably just the beginning.
HALAI: Given the increasing mosquito problem, you know, it could become a significant problem in years to come.
BORUNDA: Experts say there are a few things driving the shift. Sadie Ryan studies climate and infectious diseases at the University of Florida. She says, first of all, there are just more dengue cases all over the world right now.
SADIE RYAN: We've had several huge outbreaks happening - like outbreak years happening around the world - in a row, and we're seeing case numbers that we've never seen before.
BORUNDA: That surge in cases is probably fueled, at least in part, by climate change. Mosquito season is getting longer in many parts of the world, and more mosquitoes means more opportunities to pass the virus along. And that means more chances for a traveler to bring the virus back to the U.S, like to Los Angeles, where there are now plenty of those invasive aggressive mosquitoes to spread it along, Ryan says.
RYAN: You're basically amping-up the opportunities for biting, breeding, succeeding, you know, getting infected, and then bringing infectious in and then doing infectious bites.
BORUNDA: Climate change has also contributed to the success of those invasive mosquitoes. They have actually been introduced to California several times before, but only in the past decade has the region's climate become really hospitable for them. Experts stress that the disease can be controlled, and the most important task is controlling mosquitoes. That's why Manny Lara is out here poking around in backyards.
LARA: Hi. How are you?
UNIDENTIFIED PERSON: Good.
BORUNDA: He warns residents to drain any standing water, and he tells people to protect themselves against mosquito bites - lean into those long sleeves and bug spray. That's because three-quarters of all dengue cases are asymptomatic. So Lara says, even if you don't feel sick, it helps to avoid getting bitten, so you don't end up spreading the disease - because all the experts say it takes a village to protect the village. I'm Alejandra Borunda for NPR News.
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