There are now up to 500 million malaria cases each year, the vast majority of them in Africa. Only a small proportion of infections are fatal, but children under five and pregnant women are particularly vulnerable. Malaria is the single largest killer of young children in Africa.
Malaria is relatively easy to prevent. But many poor African countries lack the infrastructure and other resources necessary to fight the disease.
Insecticide-treated bed nets may be the cheapest and most effective tools for preventing the spread of malaria. Experts say malaria infections can be cut at least in half with the use of bed nets, since mosquitoes generally bite at night.
Still, bed nets are not widely used, mainly because of their cost and the difficulties in getting them to remote areas.
However, campaigns to distribute mosquito nets to rural areas have generated some successes. In December of last year, the UN-backed Roll Back Malaria Global Partnership combined a measles immunization campaign with the distribution of insecticide-treated nets in Togo.
As a result, 98 percent of households in Togo with children under the age of five now own at least one treated net.
"If you have a combination of political will, money, health care personnel on the ground, and the commodities you need, you can achieve swift and sharp reductions in malaria's toll," said Judith Mandelbaum-Schmid, a spokesperson for the Roll Back Malaria program in Geneva, Switzerland.
Drug resistance is another challenge. The parasite continuously mutates, making itself resistant to malaria drugs. Resistance to the drug that replaced cholorquine as the most frequent treatment is already common in eastern and southern Africa.
Meanwhile, new drugs called artemisinins, which are derived from a Chinese herb, have proved to be highly effective, and there are no signs of resistance to them yet.
But artemisinins cost several times as much as existing drugs and are not easy to produce.
The goal of the international antimalaria effort is to develop a vaccine. This has proved difficult, despite decades of research.
"While vaccines against diseases like measles and polio offer lifelong immunity, malaria is different," said Louis Miller, a malaria expert at the National Institute of Allergy and Infectious Diseases in Rockville, Maryland.
"People are repeatedly infected [with malaria over] their whole lifetime," Miller said. "The challenge is not to eliminate infection but to reduce disease. It's a completely different concept in vaccine development."
Several new initiatives have shown great promise, including a vaccine developed in a partnership between the pharmaceutical company GlaxoSmithKline and the U.S. Army.
The vaccine attacks the parasite that causes malaria as it passes through the human liver.
"The parasite is quite good at eluding the immune system," said Col. Gray Heppner, malaria researcher at the Walter Reed Army Institute of Research in Silver Spring, Maryland. "It hides out in immunologically privileged places, and it constantly changes its shape."
The vaccine was tested on more than 2,000 children in Mozambique. The results, which were published last year, show that the vaccine protected 30 to 58 percent of children against the disease for at least six months.
"The point of the vaccine is to elicit a powerful immune response that effectively attacks its Achilles heel," Heppner said.
Experts warn, however, that a commercially available vaccine is still many years away.
"It takes a long time to do testing," Louis Miller said. "We have to make sure we don't put kids at risk. If we have any impact in the next 10 or 20 years, that would be wonderful."
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