Prevention: So Many Mosquitoes, Only So Many Nets

Simple as they are, even mosquito nets generate complicated numbers games.
Only one answer is easy: more are needed.

Last Friday, as part of the first official World Malaria Day, United Nations Secretary General Ban Ki-moon called for “universal coverage” by 2010.

For simplicity’s sake, most experts go along with an estimate — that the world needs about 250 million nets at about $10 each.

That is for the current United Nations goal of having 80 percent of all pregnant women and children under age 5 who live in malarial areas under nets.

The goal is somewhat arbitrary, since the ideal would be nets for all, but that would more than double the cost.

The age 5 cutoff is used because older children usually develop some resistance through repeated infection. But some experts fear a surge in deaths of children 6 and up once they “outgrow” nets. About a million people, mostly children, die of malaria each year.

The 80 percent goal contains a safety margin: research suggests that when more than 60 percent of a village’s homes use insecticide-filled nets, mosquitoes die off instead of just biting unprotected neighbors.