The World Health Organisation’s annual report on malaria was published on December 14th. As with the report on AIDS, the picture is one of cautious optimism. Malaria is still a huge killer. Nearly 800,000 people, most of them children, succumb each year. But what was, only a decade ago, a desultory campaign against the disease now looks like a determined assault. New drugs, based on a plant extract called artemisinin, have been one arm of this assault. The other, as the chart shows, has been the spread of insecticide-drenched bednets, which protect sleepers from the mosquitoes that carry malarial parasites. The result has been a reduction in new cases of more than 50% in 11 countries in Africa, the worst affected continent, over the past ten years. Elsewhere, similar falls have been seen in 32 of the 56 countries where malaria is endemic. Overall, the number of annual worldwide deaths is estimated as 781,000 (admittedly with a margin of error of more than 150,000), down from 985,000 in 2000.