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To Fight Dengue Fever, Brazil Turns to Genetically Modified Mosquitoes

Aedes aegypti
Aedes aegyptiPhotograph by Bryan Reynolds/Getty Images

If you’re going to Brazil for the World Cup, don’t forget your insect repellent, and maybe one of these. The country has the highest incidence of dengue fever in the world, with 1.4 million cases reported last year. The disease infects at least 50 million people every year worldwide and kills over a million—the numbers have been rising in recent decades. Severe dengue was first spotted in Southeast Asia in the 1950s; it has now spread throughout Asia and Latin America. Recently it has spread to Europe. There is no cure and no vaccine.

The disease is carried by mosquitoes, mostly the Aedes aegypti. Found in urban areas, Ae. aegypti has proven a particularly difficult mosquito species to control—it has developed a resistance to common insecticides and, because it bites during the day, bed nets are no protection against it. But now Brazilian health officials are running a pilot program using genetically modified mosquitoes to breed the population to death. The mosquitoes are the invention of British biotech company Oxitec, and they’ve had a gene inserted into them that kills them. In the lab, the mosquitoes can be fed a sort of antidote: a supplement that keeps them alive until it’s time to release them. Once they’re released, the clock starts ticking.