The world is grappling with dengue epidemics, with 100 to 400 million cases worldwide every year,  an eightfold increase since 20 years ago, according to the World Health Organization. Much of this is driven by the warming climate, which allows mosquitos to thrive in more areas. 

A startup in São Paulo,  Brazil, one of the countries being hit the hardest by dengue outbreaks, has a possible solution: drones that release sterile male mosquitoes. 

Birdview has previously used drones in agriculture—releasing pest-fighting insects to make it easier to get to every corner of crop fields, which allows farmers to use fewer pesticides.

But in 2021, engineer and founder Ricardo Machado had an idea. He heard about scientists working to prevent diseases like dengue, yellow fever, chikungunya, and zika, all transmitted by the Aedes aegypti mosquito, which lays its eggs on the surface of stagnant water. 

The scientists were releasing sterile males of the species into communities with high instances of the diseases to mate with females already in the region. It’s a measure intended to curb the females’ reproductive potential, thus leading to fewer mosquitos being born, and ultimately cutting the number of cases of mosquito-borne diseases.

At the time, researchers walked or drove through affected neighborhoods, carrying canisters of sterile males and releasing them into areas that they knew were breeding grounds for mosquitoes. But there was one hurdle they couldn’t overcome: getting into the nooks and crannies of the neighborhoods where stagnant water often collects—the pool in an abandoned backyard, the tires out back at the local mechanic’s shop, the plant pots left at cemeteries.

Machado thought his drones—which could carry 17,000 mosquitoes per 10-minute flight over a 25-acre area—could be the answer to that problem.

“The challenge is getting into those hidden places,” says Machado. “It’s rare that Aedes aegypti breeding areas are found out in the open, like on a sidewalk, because when people see them, they destroy them. But with drones, we can get into areas we just can’t otherwise.”

Birdview has carried out studies with several partners since 2021, including the United Nations, the University of São Paulo (USP), and the state-owned Brazilian Agricultural Research Corporation (Embrapa), to better understand the effectiveness of releasing the disease-fighting mosquitoes with drones. First they looked at how the mechanism of the drone and outside conditions, like wind turbulence, affected the survival rate of the mosquitoes and their ability to fly.

The results were positive, so they moved on to flight-and-release tests in the Brazilian states of Pernambuco and Paraná, as well as Florida, where they’ve been working with the Lee County Mosquito Control District to see how far the mosquitoes spread upon release. They used the “mark, release and recapture” method, which involves sterile male mosquitoes being marked with a certain color before being released and later recaptured with traps so the team could see how far they had flown. They also set traps where eggs could be laid and monitored. 

“From what we’ve seen so far, our method seems to be working well,” says Machado. 

This isn’t the only attempt to use drones for the dispersal of disease-fighting mosquitoes—one team ran similar studies in Brazil’s northeast after the region saw an outbreak of zika in 2015 and 2016 that led to 3,308 babies being born with birth defects, and another is carrying out EU-funded tests in France and Spain. 

Birdview is now negotiating with different biofactories, or insectaries, that sterilize male Aedes aegypti and with others that create what are called Wolbachia mosquitoes—Aedes aegypti injected with the Wolbachia bacteria can no longer transmit viruses like dengue—in hopes of creating partnerships so it can bring its technology to other countries.

“The mosquito is the deadliest animal in the world,” says Machado. “We want to work with as many insectaries as possible. This doesn’t have to be used just to fight the Aedes aegypti mosquito and the diseases it spreads. It can be used to fight malaria too.”

But for some experts, scaling up Birdview’s model and getting that technology to other countries—especially those that are low and middle-income—could become an obstacle.

“It’s a method that sounds promising, but we still need to better understand the costs involved,” says Neelika Malavige, head of Dengue Global Program and Scientific Affairs at the Drugs for Neglected Diseases Initiative (DNDi). “We need to know how affordable it will be to use this technology and how it can be relocated to other countries.”

Machado says the UN has previously given financial support to low-income countries for similar projects and hopes that it and other organizations will continue to do the same with this one.

He also notes the importance of decentralizing the work done with the drones by training at least one pilot per community using the mosquito-releasing technology.

“We don’t want anybody to have to rely on Birdview or any other company to do this work,” says Machado. “We want to be able to hand them the tools they need so they can be the ones to protect their own communities.”