Here on the shores of Lake Victoria, hundreds of communities have discovered a potential key to curbing the African AIDS epidemic: Laws can sometimes make progress where doctors and health workers alone have failed. In the past few years, local governments and village councils have cracked down on a variety of traditional social and sexual practices that had made this area literally a breeding ground for HIV. Mwalinha, population 2,650, a dusty scattering of mud-brick huts and cassava fields, has outlawed dancing after dark, and women can't be served alcohol after 6 pm. The village of Itumbili, several kilometres down rutted roads, recently banned a particularly hazardous harvest rite called chagulaga meaning "choose," which involves men chasing unmarried women into the bush and coupling for the night. Another village, Nyakaboja even made it a crime to flirt, punishable with the payment of a chicken. For the most part, the new laws arose from an innovative research project funded by the Dutch government.Originally, the project's goal was simply to draw up maps of 900 villages and neighbourhoods in Magu district, covering 4,810 square kilometres, pinpointing dance clubs, abandoned huts and other likely hotspots for HIV transmission. Gradually, however, village leaders began using the maps to create legislation aimed at nothing less than a grassroots transformation of their culture.

Now, Magu has become something of a Mecca for health professionals scrambling to stop the spread of a disease that has already claimed 17 million lives south of the Sahara-nearly 80% of the global AIDS toll. More than 200 AIDS experts from all over the world have descended on the area in recent months, and other districts in Tanzania are attempting to replicate the programme. "It's survival of the smartest," says Reuben Ole-Kuney, commissioner of Magu district.

So far, It's not clear whether the patchwork of village rules has actually reduced the HIV infection rate, which measures 12% among blood donors at the Magu District Hospital. Health workers consider that sample group typical of the adult population in larger towns. And it's hard to say whether Magu's experience could be successfully duplicated elsewhere-particularly in urban areas where people don't know each other well and may be less susceptible to peer pressure.

What is more, AIDS experts say, helping overhaul a scattered system of social codes can be enormously labour-intensive and time-consuming.Still, some early evidence is encouraging. A survey by the Dutch group indicates that 38% of Magu district residents see safer behaviour in their villages. Teachers report a decrease in pregnancies among schoolgirls, a sign that youths are having less sex or using more condoms.

"A while back, we caught people all the time returning from the well or the mill at night," says 48-year-old Mohamed Athuman, chief of the village militia in Mwalinha. "Nowadays, people are trying to be more careful."Such caution is often enforced at the end of a stick. In Tanzania, punishment for social violations is meted out by militias-called sungusungu, after the region's aggressive army ants-equipped with bows, spears and clubs. Though endorsed by the national government and overseen by village councils, militiamen wear no uniforms and receive no pay, and usually take a cut of the fines they impose on village scofflaws. "Sometimes we beat them with a club, if they're rude," says Boniface Sengerema, a 39-year-old commander of the Mwalinha militia. "If they repeat the same offence, the penalty goes up. If it was one stroke with a club, it goes to two strokes."In Ms Saidi's case, the sungusungu fined the couple 1,000 shillings ($1.25) each, roughly a day's earnings at her small medical-supplies shop. "You live here, you know the laws," Ms Saidi recalls the sungusungu telling her. She immediately confessed to her carnal intent-thus avoiding the beatings delivered to the unrepentant-and promised not to repeat the offence.

Ms Saidi, who is 34 years old and divorced, says her partner paid both shares of the fine, but fled without giving her the 10,000 shillings he had promised. Even worse, her family was embarrassed and angry with her. "I thought there wouldn't be any patrols out," she says, averting her gaze and covering her mouth with the collar of her tattered shirt.

The Dutch-funded research group, the Tanzania Netherlands BSupport Programme on AIDS, got its stars in a joint effort by the two countries to study the spread of the virus. The group decided to focus on Magu because it has particularly poor health-care services, even for Tanzania. Magu District Hospital has just one doctor and no X-ray machine. Many people here never know or won't admit they have AIDS. Some who do know don't bother seeking treatment or use traditional healers. And the average resident earns just $70 a year, meaning that few can afford standard medical care., much less than the expensive drug cocktail that had been extending lives in rich countries. Also, the district's demographics seem particularly ripe for AIDS transmission. Magu is home to hordes of itinerant fishermen who catch HIV in rural lakeside brothels. Overall in this rural district of 415,000 people, more than 2,000 are believed to have contract the virus each year-a rate comparable to the rest of sub-Saharan Africa. In thegreater Mwanza region, which includes Magu district, one in three deaths is caused by AIDS.

The researchers, who included mostly Tanzanians and some Europeans, started their project by asking villagers-in separate groups of men and women-to draw maps identifying the most likely places for HIV transmission. The men usually marked the local bar, the guesthouse and the dance club. The women often added the school, the church, the well, and the forest, suggesting the prevalence of rape in isolated places and sexual abuse of schoolgirl by teachers. Once the maps were completed, men and women sat down together and compared notes. These gatherings of roughly 10 to 15 people often led to unprecedented public discussions of sexual practices and the dangers of AIDS. Then, guided by a village leader or a health worker trained by the researchers, the groups began suggesting ways of bringing local statutes to bear on the HIV plague. Sometimes, the groups proposed laws to existing village organisations, such asthe social-services committee. The villages also formed school AIDS committees to draft rules relating to students.

Sample: Students are barred from attending pornographic-video shows put on by travelling entrepreneurs who charge for admission. Ultimately, the proposals went to the village council for consensus approval.