ABSTRACT
AIDS in Africa has bewildered the West for decades. It seems to act like a different disease there, striking a new array o f victims and spreading far beyond its silos in the West. From the outset people have wondered, Why is African AIDS mainly heterosexual? And why are the infection rates so astronomical in some parts? The answer is subtle and still eludes many: it's all about networks. To most people's sur prise, HIV is actually hard to transmit-much, much harder than, say, gonorrhea and other common STDs. For heterosexuals the risk per act of intercourse is around one in a thousand, or even less. Infection thus usually requires a great many acts-and a person is far more likely to get HIV from an ongoing partner than from a prostitute, if both have it. Hence multiple concurrent partners, such as married sugar daddies with mistresses, raise the risk. More risk from one's regular partner than from a prostitute? This goes against our gut instinct, centuries of thought, and even biblical wisdom. But if multiple, concurrent part nerships are common, sexual networks can take shape.
