For Africa, the epicenter of the world’s malaria scourge, an historic breakthrough in health and economic development is now within reach. A combination of new technologies, new methods of disease control and rising public awareness is poised to bring malaria deaths down by 90 percent or more—if we will follow through.
The killer form of malaria is caused by the protozoan Plasmodium falciparum, which is transmitted by the bite of the anopheles mosquito. Because of the life cycles of the pathogen and of the mosquito, an ambient temperature of at least 18 degrees Celsius (65 degrees Fahrenheit) is needed for transmission. Higher temperatures raise the chances of transmission, which is why malaria is mainly a tropical disease. The extent of transmission is determined by the abundance of mosquitoes, the ambient temperature, and the propensity of specific anopheles species to bite humans rather than animals. Africa’s ecology in all three respects makes the force of infection higher than in any other part of the world.
Efforts at malaria control in the 1950s and 1960s successfully used the insecticide DDT and the medicine chloroquine to eliminate the disease in many temperate and sub-tropical regions. But malaria persisted in the tropics and especially in Africa, where the intensity of transmission is the world’s highest for ecological reasons. Africa pays a fearful price for its ongoing malaria burden, not only in more than one million deaths each year but also in significantly reduced economic growth.
Until very recently, things were getting worse, not better. The malaria parasite became widely resistant to chloroquine. Confusion over DDT’s prudent anti-malaria application (sprayed as a thin film on the inside walls of houses) and its function as an insecticide in open fields (which is environmentally unsafe and promotes resistance) also curtailed use of the chemical.
The most promising long-term solution is a vaccine, and exciting candidate vaccines are now in clinical trials. Yet even as we await a vaccine, a confluence of advances gives a chance for a breakthrough in the near term. The first is the invention of long-lasting insecticide-treated bed nets, which protect sleeping individuals against indoor nighttime biting. These nets last for five years, unlike earlier nets that needed re-treatment every few months.
The second advance, which can save countless lives, is a new generation of highly effective medicines based on artemisinin, an herbal extract discovered by Chinese scientists. (Artemisinin should be used only in combination with more traditional drugs, however, to prevent the onset of resistance in parasites.)
The third advance is a new approach to disease control. In the past, the U.S. government and other donor agencies favored the sale of bed nets at a discount. The result was a very slow uptake of the nets because most African rural households were too poor to buy them. Moreover, the discounts were targeted only for young children and pregnant mothers, the groups most likely to die from malaria. That targeting policy neglected a crucial point: unprotected individuals serve as reservoirs for malaria infection, not only becoming sick themselves but facilitating transmission back to the “protected” groups because the nets are not 100-percent effective.
The new strategy is based on mass free-distribution of nets, with one net for every sleeping site. Everybody is protected from illness and no group is left as a reservoir for transmission. The artemisinin-based medicines should also be available for free within the villages. This approach is highly affordable for donor countries, because the cost of each net is only $5, and each treatment dose of medicine about $1. Free distribution of nets is already being applied successfully in several impoverished countries.
Malaria control is the bargain of the planet. A study that my colleagues and I undertook recently showed that comprehensive coverage of nets and medicines, and indoor insecticide where advisable, can be accomplished for $3 billion per year in the next few years, which equals just $3 from each person in the high-income world. Or to put it another way, the equivalent of two days of Pentagon spending could save more than a million lives per year. And these costs will come down in later years as infection rates decline. In addition to the lives save, the economic gains in Africa would soon amount to tens of billions of dollars per year, manifested in direct reductions of the cost of illness and increased economic growth.