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.