Kill or be killed

Malaria takes one child every 30 seconds and costs billions to combat; but unless the mosquitoes die . . . they will find a way in | Priya Abraham, Marvin Olasky

In Africa, mosquitoes go blood hunting after dusk. They often drift in through open windows or doors, but any crack or crevice will do. Inside, they sniff out their prey: a mother scrubbing pots after dinner, a child's ankles as she finishes her homework.

Bedtime is the best time for feeding. Through the quiet darkness comes a mosquito's reedy whine when it zips past your ear. But in Africa mosquitoes mean more than itchy bites; just one can bring death through malaria. And trillions breed anywhere there is fresh standing water, even puddles.

Sleepers sometimes use insecticide-treated bed nets as a defense—the nets often hang over floor mats, not beds—but the mesh turns stifling in the heat. Badly hung nets have gaps, and any tear renders them useless. Trying to stop every mosquito is a dead man's game: They will find a way in.