Safe-sex messages have not stopped. If anything, they are harder-hitting.

A recent one features the leering face of a creepy middle-age man. “You wouldn’t let him sleep with your teenage daughter,” it says. “Why are you sleeping with his?” Another shows a frightened child saying, “My mommy is sick because of the sexual network.”

Many Africans, researchers say, are in one or more relationships that may include sex only infrequently but last for years. Some are open, as in polygamy; many are clandestine, as with old lovers, bosses or even, perhaps, an abusive uncle who cannot be shaken off.

In such networks, infections spread rapidly. Also, men here, like many men everywhere, complain about condoms.

The arrival of AIDS drugs let some go back to old habits.

“When you are sick, you are tired, you are impotent,” said George Bitti, 58. “But when you are on the drugs for a certain period, you become strong, you regain your body. And you start going again for sex.”

But even before drugs arrived, powerful societal forces were arrayed against safe sex.

“According to African culture, the man is the overlord,” said Peace Atwongyeire, 42, a handsome counselor whose face adorns local billboards saying she is not ashamed to be H.I.V.-positive. “You have to say yes.”

Because a man buys a wife from her father for cows or cash, he “owns” her. If she refuses sex or insists on a condom, he may beat her or throw her out of the house.

Also, condoms thwart pregnancy, and “I prove my manhood by having children,” said Mr. Bitti, a father of 14. “That is how a girl proves she is a woman. In Africa, you cannot tell anyone to stop having children. They will even think, ‘I would rather have AIDS and leave my children when I die. At least I will have produced my three.’ ”