Every year, more than 450,000 people, mostly children, die of malaria. The disease is caused by single-cell parasites and spread by mosquitos. Although parasites have developed resistance to artemisinin in many countries, when used in combination with other drugs it reduces malaria deaths by about 20%, the committee said. "For Africa alone, this means that more than 100,000 lives are saved each year."

In the 1970s, Omura, a microbiologist, screened thousands of soil samples for new strains of Streptomyces, a bacteria that was known to ward off other microbes. He identified 50 of those strains that seemed most promising, which Campbell, who was then working at the drug company Merck, tested in animals. Campbell discovered that o­ne of them was an especially good parasite killer, thanks to an ingredient called avermectin. Later o­n, the researchers modified avermectin into a more powerful compound called ivermectin, which is now widely used.

In the late 1960s, the Chinese government launched a project to find treatments for malaria, and Tu became one of its scientific leaders. "During the first stage of our work, we investigated more than 2,000 Chinese herb preparations and identified 640 hits that had possible antimalarial activities," she wrote in 2011. Tu discovered that an extract from the sweet wormwood (Artemisia annua) plant seemed to help treat malaria in animals, and later narrowed it down to o­ne of the plant's compounds, artemisinin. "During the Cultural Revolution, there were no practical ways to perform clinical trials of new drugs," Tu wrote. "So, in order to help patients with malaria, my colleagues and I bravely volunteered to be the first people to take the extract."