"I've been applying my imagination to the synergies of this," he said. "We could have sorghum that cures latent tuberculosis. We could have mosquitoes that spread vitamin A. And most important, we could have bananas that never need to be kept cold."
They laughed. Perhaps that was to be expected when the world's richest man, who had just promised them $450 million, was delivering a punchline. But it was also germane, because they were gathered to celebrate some of the oddest-sounding projects in the history of science.
Their deadly serious proposals - answers to the Grand Challenges in Global Health that Mr. Gates posed in a 2003 speech in Davos, Switzerland - sounded much like his spoofs: laboratories around the world, some of them led by Nobel Prize winners, proposing to invent bananas and sorghum that make their own vitamin A; chemicals that render mosquitoes unable to smell humans; drugs that hunt down tuberculosis germs in people who do not even know they are infected; and vaccines that are mixed into spores or plastics or sugars and can be delivered in glasses of orange juice or modified goose calls.
What Mr. Gates had outlined at Davos were the greatest obstacles facing doctors in the tropics: Laboratories are few and far between. Vaccines spoil without refrigeration and require syringes, which can transmit AIDS. Mosquitoes develop resistance to all insecticides. Crops that survive in the jungle or desert often have little nutritive value. Infections outwit powerful drugs by lying dormant.