Blanching at the stench of urine, I stumble up pitch-black, uneven steps to the top floor, which seems to be a rooftop on which someone has constructed shacks out of brick, asbestos and plastic. A shaft of light from a street lamp falls past tenuous bamboo railings onto a figure in a glittering white sari. She crouches on the bare brick floor by the roof's edge, holding a mirror in one hand and a lipstick in another, using the light to make up. Older residents of the brothel, who expect no clients, crowd into a tiny room to tell me their stories. "I've spent my life in this hell," says Pushpa Adhikari, an ancient woman with sad eyes who was sold into sexual slavery at the age of nine. The others demur: thugs used to terrorize the brothels with nightly rapes and murders, but now that the prostitutes are united the hoodlums keep their distance. "It used to be hell--now it's heaven," corrects one woman, and even Adhikari nods.

Freeing the brothels from terror is merely a side effect of the Sonagachi project, an HIV intervention program named after the red-light district of Kolkata (formerly Calcutta) where it began. Rural poverty forces millions of Indian men to migrate to urban centers in search of a livelihood; there they visit brothels, pick up the AIDS virus and take it back to their wives. Truck drivers also infect prostitutes along the major highways. India already harbors at least five million cases of HIV--the most in the world after South Africa--but it is too poor, and its health infrastructure too weak, to permit reliance on drugs. Only if prostitutes cease to acquire and transmit the virus can the epidemic be contained, and Smarajit Jana, a public health scientist, has found a way to accomplish that.

"I strongly believe that for a program to succeed, the subjects have to adopt its goals as their own," he explains. They have: the sex workers run the HIV program themselves. Jana persuaded them to form a growing collective that now includes 60,000 members pledged to condom use. It offers bank loans, schooling for children, literacy training for adults, reproductive health care and cheap condoms--and has virtually eliminated trafficking of women in the locale. Best of all, the project has kept the HIV prevalence rate among prostitutes in Sonagachi down to 5 percent, whereas in the brothels of Mumbai (Bombay) it is around 60. Other sexually transmitted diseases are down to 1 percent. Jana now works with CARE in Delhi, assisting other social workers in similarly transferring their HIV prevention programs to the people they serve. Such community-led interventions have become integral to the Bill and Melinda Gates Foundation in its five-year, $200-million effort to combat AIDS in India.

An unassuming man with flyaway hair and a ready smile, Jana, who is now 53, went through medical school in Kolkata in the 1970s. There he organized students to collect leftover medicines and visit slums to treat the inhabitants. Medical school in India is highly subsidized, so "we felt very strongly that we were morally responsible" to give something back, Jana recalls. They campaigned and litigated against hazardous medical products, getting two dozen of them recalled. When, instead of aiming for a lucrative private practice, Jana specialized in public health and went off to run a rural clinic, his parents were horrified.

At the clinic, Jana observed that if a woman had undergone a tubectomy, for which she had received money from a population-control program, she invariably blamed any subsequent health problems on it. Circumstances having forced her into the operation, she resented it and influenced others against it. "In the short term, you can get results with such coercive methods," Jana realized, "but in the long term, the program will fail"--as, indeed, the sterilization effort did. To truly succeed, one needed not only informed consent but heartfelt consent, which meant that one first had to understand what made someone tick.

Jana would apply this insight in 1991, when an official from the World Health Organization asked him to survey the brothels of Sonagachi for HIV. By then, Jana had found his niche in occupational medicine, establishing precedents for compensating factory workers and protecting tea-garden laborers from pesticides. Jana agreed to the WHO request only after the official used the phrase "sex worker": the concept intrigued him. He opened a clinic in the area, and when patients finally trickled in, he treated and listened. The prostitutes' lives turned out to revolve around their children, which suggested how to make HIV relevant. Jana in turn explained to the women that he saw them simply as workers earning a living: "I sell services, so do you." To the prostitutes, who despised themselves no less than everyone else did, the idea was mind-boggling. "Many others came to ask if I had indeed said this. It had a ripple effect," Jana remembers. Gaining a measure of self-respect became the first step in a long process of empowerment.

Following the survey, Jana undertook to ensure that the women protected themselves against HIV. He trained a few sex workers to go around the brothels talking about the virus and distributing condoms, and he sent researchers along to take notes on everything. It transpired that if a prostitute insisted on condom use, her customer just went to someone else. Unlike AIDS, starvation posed an immediate threat, and the program seemed doomed. "Counseling, educating--it just doesn't work," Jana states. "Higher up in the social hierarchy, people are able to act on the information given to them. Not so in the lower levels."

Thinking of HIV as an occupational hazard gave him the solution: a workers' collective. "The outcome of a negotiation depends on the relative power between the two parties," Jana explains. "When an individual sex worker deals with a client, she is weak. To change the power equation, she needs the support of other sex workers."

That was not enough, however: Jana also had to loosen several layers of coercion that perpetuated unsafe sex. He persuaded the brothel madams that keeping HIV down was in their interest. To reduce the depredations of gangsters, he invited their bosses--often local politicians--to tour the area and converted them to the cause. He lobbied the police to stop raiding brothels, because if a prostitute lost a day's earnings she was less likely to insist on condom use. He argued with syndicate leaders who controlled the pimps and who ultimately conceded to his economic logic. And finally, because society's revulsion left the sex workers feeling worthless and therefore less able to protect themselves, Jana pitted them against Kolkata's intellectuals in impassioned, face-to-face debates about morality. As the women grew in confidence, he removed himself from the scene: Jana's greatest achievement is his planned obsolescence.

Jana has added community empowerment to the known spectrum of structural interventions--that is, programs that seek to alter the forces that maintain harmful behavior, explains public health scientist Michael Merson of Yale University. The United Nations's AIDS effort holds the Sonagachi project up as a "best practice" model. Still, how well it can be reproduced remains to be seen. Meanwhile the collective has hosted three conferences, attended by sex workers from around the world (including the U.S.) who hope to learn its secret. And while I interview Jana during one of his visits to Kolkata, hundreds of women wait patiently outside, each for her turn to meet him. In their eyes, this man who reached down to help them up wears the halo of a modern-day savior.