Botswana seems an unlikely place for an AIDS epidemic. Vast and underpopulated, it is largely free of the teeming slums, war zones, and inner-city drug cultures that epidemiologists say are typical niches for the human immunodeficiency virus. Botswana is an African paradise. Shortly after gaining its independence from Britain in 1966, large diamond reserves were discovered, and the economy has since grown faster—and for longer—than that of virtually any other nation in the world. Education is free, corruption is rare, crime rates are low, and the nation has never been at war. Citizens are loyal: A visitor quickly learns that even mild criticism of anything related to Botswana is considered impolite. Yet this country, with all these advantages, has the highest HIV-infection rate in the world.
The virus has spread extremely rapidly in Botswana. Two decades ago, virtually no one there was HIV-positive. By 1992 an estimated 20 percent of sexually active adults were infected. By 1995 that proportion had reached one-third, and today it is roughly 40 percent. In Francistown, Botswana’s second largest city, nearly half of all pregnant women in the main hospital test positive for HIV. The picture in the rest of sub-Saharan Africa is nearly as dire. AIDS has killed Zulu nurses in South Africa, Masai teachers in Tanzania, Kikuyu housewives in Kenya, Pygmy elders in Uganda. HIV infection rates range from around 6 percent in Uganda to 39 percent in Swaziland.
Such numbers are astronomical compared with most of the world. In the United States, less than 1 percent of the population is infected; in Russia and India the figure hovers around 1 percent. Even in Thailand, with its thriving sex and drug trades, the proportion of infected barely exceeds 2 percent.
The high rates come despite efforts in many communities to stem the HIV epidemic through educational programs, condom distribution, and treatment for such sexually transmitted diseases as gonorrhea and syphilis, which create genital sores and ulcers that make it easier for the virus to spread. In most cases these programs have had little effect. The growing disaster has forced AIDS experts to reconsider old theories about how HIV spreads in Africa.
Outside of sub-Saharan Africa, many HIV-positive people are injecting drug users, prostitutes, and highly promiscuous homosexual men who may have hundreds of different sexual partners every year. But most Africans with HIV claim never to use drugs, engage in prostitution, or have large numbers of sexual partners. To explain the high infection rates, scientists have advanced theories ranging from nutritional deficiencies to more virulent HIV strains to different sexual customs. In the 1980s Australian demographer John Caldwell insisted that the virus was spreading rapidly in Africa simply because people there tended to have more sexual partners than people elsewhere. He pointed to the cultural desire for many children, the tradition of polygamy, and other aspects of African society that contributed to a greater tolerance of promiscuous behavior than in the West. Caldwell’s views sparked controversy and for years received little attention. Recently, though, some experts, including epidemiologist James Chin of the University of California at Berkeley, have revisited the theory. Chin believes it’s the only possible explanation: “People tell me not to say it, but I strongly believe it.”
Some studies do show that Africans have more—but not vastly more—sexual partners, on average, than people in Western countries. For example, a study of sexual behavior in Zimbabwe, where roughly 33 percent of adults are HIV-positive, found that in a single year, most people have between one and three sexual partners. Of course, prostitutes in Zimbabwe may have more than 100 partners a year, just as prostitutes elsewhere in the world do, but most HIV-positive Zimbabweans are not prostitutes.
In the early 1990s, Martina Morris, then a member of the sociology and public-health departments at Columbia University (and now a professor of sociology and statistics at the University of Washington in Seattle), tried to solve the mystery of HIV in Africa mathematically. She had helped devise a computer program to predict the spread of HIV in a given population based on such factors as the number of sexual partners people had and the duration of those relationships. At the time, Uganda had one of the highest HIV-infection rates in the world, so she flew there in 1993 to gather data on sexual behavior.
“Just after I arrived in Uganda, I had to give a lecture to Ugandan doctors at the medical school in Kampala, telling them what I planned to do,” she recalls. “At the time there was talk in Uganda about helicopter scientists—whites from the United States and Europe who just parachuted in, took data, and didn’t work with local African experts. I was the only American woman in the room, and it was a tough audience. The HIV rate was estimated to be 18 percent at the time, and here I was trying to explain how mathematical models were going to help. They listened, and then at the end, one man raised his hand and asked, ‘Could your model handle more than one partner at a time?’ I said, ‘No.’ The man walked out. The others sat down with me and said I had to include concurrent partnerships in my model. Otherwise it would be irrelevant.”