The mosquito Aedes aegypti is infamous for carrying Zika and dengue fever. The quest to kill it has consumed enormous amounts of money, time, and effort. So it seems counterintuitive that a team of scientists and health workers have just received $18 million to release these mosquitoes over densely populated parts of Brazil and Colombia.
Their insects are no ordinary mosquitoes, though. They’ve been implanted with a bacterium called Wolbachia, which stops them from spreading the viruses behind Zika, dengue, yellow fever, chikungunya, and other diseases. It's not totally clear how it does this, but it may be by competing with the viruses for nutrients or boosting the insects' immune system. With this microbe inside them, the mosquitoes are no longer carriers of sickness. They are dead-ends.
Better still, Wolbachia also excels at spreading through a population, manipulating its hosts to maximize its chances of entering the next generation. If you release small numbers of Wolbachia-infected mosquitoes over a region, within a few months, almost all the local insects should carry the microbe and thus be unable to spread several human diseases.
I wrote about the history of this approach, and the science behind it in my recent book, excerpted in The Atlantic back in August. It’s the brainchild of Scott O’Neill from Monash University, who has been working on it since the 1980s, despite a vexing succession of problems. “It’s probably a personality disorder on my part, not being able to let go,” he says. For example, it took several decades for his team just to introduce Wolbachia into mosquito eggs—a process that’s like slipping a needle into a balloon and then pulling it out without popping anything.