Darfur is just 500 miles north of N'zara, where scientists believe the often lethal West Nile virus (which has now spread to nearly every state in the United States) resides. In 1976, N'zara also was the site of a major outbreak of the deadly Ebola virus. And across Sudan's southern border, Uganda is believed to be ground zero for the global AIDS epidemic. The circumstances of West Nile's spread remain a mystery, but the Ebola outbreak and the AIDS epidemic owe a great deal to the treacherous mixing of war, refugees and microbes.

As for HIV, it also can be traced to the 1970s and another ethnic- cleansing campaign in the same region of Africa. Ugandan strongman Idi Amin set his soldiers against tribes in the Rakai district, with rape as a primary weapon. When the conflict spilled over into Tanzania, so did the rape, and when Tanzania's army repulsed Amin's forces, it carried out its own campaign of rape in turn. As it happened, however, another form of revenge spread along with the rape: HIV.

Today, as then, a chief horror of the Darfur campaign is the militias' raping of women and girls. They brand their victims' foreheads so that all will know that the women and their potential offspring are tainted. Nobody knows how prevalent HIV is in the Darfur region (Khartoum has never allowed surveys of the area). In the Muslim north, surveys of pregnant women four years ago revealed that 3% of them were HIV-positive; a N'zara-area survey found infection rates twice as high. It isn't unreasonable to suspect that the current Darfur "ethnic cleansing" campaign is spreading the disease, not only among the people of Darfur and their janjaweed rapists but also among refugees in camps in neighboring Chad. It is equally reasonable to posit that some other previously obscure sexually transmitted disease could be amplified to epidemic proportions via the bodies of the women of Darfur.