DEPENDING on one's perspective, the struggle to gain dominion over malaria can be seen either as a primer of the possible in infectious-disease control or as classic tragedy. All but obliterated in the developed world half a century ago, and suppressed in the Third World in the 1950s and 1960s, malaria has since returned in full force to North Africa, India, Southeast Asia, China, South America, and the Caribbean. Worldwide incidence of the disease has quadrupled in the past five years, and resistance to available drugs for prevention and treatment is growing rapidly. Nearly 40 percent of the world's population lives in regions where malaria is endemic, and millions more live in areas that are encountering the disease for the first time in decades. Europe has had outbreaks, and in the United States 1,000 to 1,200 cases annually have been reported in recent years. But the Centers for Disease Control and Prevention estimates that cases reported in the United States represent only about half the actual incidence. Every year approximately seven million American tourists and business people spend time in regions where malaria is endemic, as do military personnel and foreign visitors to the United States, and it is likely that thousands arrive here with malaria parasites in their bodies. As a consequence, locally transmitted malaria, absent from the United States for roughly thirty years, has returned. Since 1988 locally transmitted malaria has appeared in California, Texas, Michigan, Florida, New Jersey, and New York City. Anopheles mosquitoes -- members of the genus that carries malaria parasites -- are common almost everywhere in the United States and, for that matter, in most populated regions of the world.
Nonetheless, the United States has shown little interest in the problem. Malaria is transferable in blood, yet it is not screened for in the American blood supply. The country's Anopheles mosquito population has gone unmonitored for more than fifty years. "We just don't know the potential for transmission," says John Beier, a professor of tropical medicine at Tulane University. Temperature and humidity may well be among the most important factors in the rate of spread of the disease, yet we have only a vague notion of what effect, if any, climate change will have on malaria transmission -- if, for example, global warming can be expected to bring malaria and other mosquito-borne diseases north from Mexico. Most Americans seem to think the disease has been eradicated or, at worst, is confined to the tropics. In fact there are few places on earth that cannot sustain a malaria epidemic.