The world's deadliest animal is not the great white shark, or the grizzly bear, or even the moose. It's so small you can easily flick it away or even squash it. Yet the mosquito, by spreading pathogens, kills more than a million people every year, and sickens hundreds of millions more. To underscore just how dangerous they are, Bill Gates recently released mosquito-related posts during what he dubbed "Mosquito Week," a takeoff on Shark Week. "Mosquitoes and the diseases they carry kill more people in one day than sharks kill in 100 years," Gates noted in an email to his blog subscribers.

The worst thing by far that people catch from mosquitoes is dengue fever, which kills 20,000 people a year and makes another 400 million sick. But there's also the Zika virus, West Nile virus, chikungunya, and yellow fever. What many of us think of as an annoying summertime pest can actually be a deadly threat, especially in tropical climates.

What is Gates doing about it? Strangely enough, he's supporting a program that's breeding more mosquitoes and releasing them in 11 countries, mostly in Southeast Asia and South America. These mosquitoes are infected with Wolbachia bacteria, which blocks them from transmitting the diseases that kill people. As the lab-raised mosquitoes breed with other mosquitoes, Wolbachia spreads through the mosquito population, making them decidedly less deadly. In a pilot program in Indonesia, releasing Wolbachia mosquitoes cut dengue fever infections by 77 percent. People may be getting just as many itchy mosquito bites as they were before, but fewer of them are dying.

For obvious reasons, Gates writes, the idea of breeding mosquitoes and releasing them to bite unsuspecting people didn't go over well at first. But the results of the pilot have been impressive enough that now the biggest challenge is breeding enough Wolbachia mosquitoes to supply all the places that want them. 

Using sugar to kill mosquitoes

We all know that mosquitoes love human blood, and we have the bumpy, itchy bites to prove it. But, it turns out, mosquitoes need sugar throughout their lives so they can have enough energy to fly, whereas only mosquito mothers seeking food for their larvae seek human blood. 

So another initiative Gates calls out in his blog is one that uses a simple combination of sugar and insecticide to attract and then kill mosquitoes. The bait is behind a membrane only mosquitoes can penetrate, so while it may attract other, more beneficial insects such as bees or butterflies, it won't kill them. The baits are inexpensive to produce, small, lightweight, and easy to nail to an outside wall, Gates writes.

Right now, the sugar baits are at the development phase. Research shows that, combined with the bed netting and indoor insecticides already in common use, sugar baits could significantly reduce mosquito populations around homes, and thus reduce the incidence of malaria by 30 percent in places where it is widespread. There were 241 million cases of malaria and 627,000 deaths from it in 2020, and those numbers keep rising, so a 30 percent reduction could save hundreds of thousands of lives. Who knows? Maybe someday we'll all have them hanging outside our homes.