It's noon and the prostitutes are sitting together on a bench in a cool dark hallway in Dakar, the capital of Senegal. Many are wearing the country's traditional robes of colorful patterned cloth, but others are dressed more like Americans, in dirty sneakers and shirts emblazoned with the Nike swoosh. There's no makeup, short skirts, or hustle. It looks, in fact, a bit like a morning at the Boston DMV. And they are lined up for much the same reason that folks head to the DMV: to be tested, in order to make sure that they can keep their licenses.

Prostitution was legalized in this predominantly Muslim country in 1969, and today the government tolerates it as long as each prostitute registers with the state, is over 21 years old, and comes regularly to a center run by the Ministry of Health for checkups, education, and medical treatment. And that's a big reason why this West African nation of 10.5 million, according to the World Health Organization, has an HIV infection rate of about two percent while many of its nearest neighbors face rates several times higher; some Southern African countries, such as Botswana, report that a mind-boggling 39 percent or more of the adult population is infected.

As University of Notre Dame physicist Albert-Lszl Barabsi sought to demonstrate in his recent book "Linked: The New Science of Networks," an epidemic like AIDS spreads, to a large degree, from a very small number of individuals. Most sexually active young men and women have only a handful of partners in a given year; but a few, including many prostitutes, have hundreds. And as in other networks, like the World Wide Web, these "hubs" bear the lion's share of responsibility for connecting everyone else-which in this case means spreading the disease. Educating one typical young man or woman about AIDS might save five additional people. But educating and protecting a single prostitute might save thousands, or even more.

In the United States, epidemiologists traced much of the crisis in the early 1980s to Gaetan Dugas, the so-called "patient zero," a French-Canadian airline steward who had sex with thousands of men. In East and Southern Africa, AIDS probably first spread outward from the so-called "AIDS Highway," where truckers would stop to meet with prostitutes as they drove their loads from South Africa to Kenya.

Senegal is desperately trying to stop infections from spreading among people who could serve as hubs by regularly checking prostitutes for AIDS and other sexually transmitted diseases. If they are HIV-positive, they have the option of government-funded treatment. If a prostitute is discovered to have an STD, she will lose her little green license card until she's finished treatment, largely because infection with one STD dramatically increases one's risk of contracting HIV. This program is similar to one in the state of Nevada, where prostitutes are tested and screened for AIDS and other STDs before they are licensed to work. But where Nevada bans HIV-positive prostitutes from working, Senegal allows most of them to go back on the streets after undergoing additional AIDS education. Banning HIV-positive prostitutes, the government's reasoning goes, would both stop these women from coming in for checkups and increase illegal, unregulated prostitution.

"We decided that if we could keep the rate low in the core groups, it would be very good for Senegal," says Anton Meyer, the French doctor in charge of the prostitution program, which is funded by the Senegalese government and by international health organizations. "It's an enlightened public health approach," says Richard Marlink, executive director of the Harvard AIDS Institute, who has been working with Senegal on AIDS prevention and awareness for 15 years.

And the program is working. Fewer than 15 percent of the women who come to the center test positive for HIV. Furthermore, all of the women at the center know the stakes of the disease, quite an achievement on a continent where many people believe, for example, that sex with a virgin will cure AIDS. Educating even a few prostitutes about AIDS helps spread information throughout the profession, even to those women who've never been to the clinic. "I try to give advice to as many others as I can so that they should come here if they want to stay healthy," says Khaly Sall, a Senegalese woman who has been working as a prostitute for 30 years, and has been coming in for government checkups almost since the very beginning-although she claims she's never had an STD.

"I know about the risk of AIDS because I have seen friends who've had it. That's why I come here," says Veronika Igbinoria, a 22-year old Nigerian prostitute who came to Senegal two years ago and says she absolutely never has unprotected sex now. "If a man comes up to me and says he doesn't need to use a condom because he is paying, I say, 'Do you know whether you have the sickness? Do you know me and whether I have it? You don't.'"

There are problems, of course. Many prostitutes operate clandestinely for fear of stigmatization, and those who are younger than 21 are unable to register or use the government clinics. While some argue that legalized prostitution only encourages the practice, the question may be moot: There is just too much poverty and too little funding for law enforcement to make a dent in the number of women selling their bodies anyway.

Senegal's prostitution program is a major reason why the spread of AIDS has slowed in that country, but it isn't the only reason. A forward-looking government recognized the magnitude of the problem back in 1986; Senegal's moderate Muslim and Christian leaders have worked together to improve education; and organizations such as the US Agency for International Development (USAID) have thrown money, condoms, or both at the problem. "I have enough condoms in my home for one year," says Diasse Ibrahima, one of Senegal's biggest basketball stars. "I saw someone on TV with AIDS and I thought, 'I never want to get that.'"

But many other countries have similar programs and much higher infection rates. Even the Gambia, a tiny sliver of a nation surrounded by Senegal on three sides, has a higher rate of AIDS infection. Senegal has simply been smart and original in recognizing that prostitution exists, that it feeds the epidemic, and that it's better to deal with this problem instead of ignoring it. While African nations have watched average life expectancies fall by up to 20 years, Senegal is able to post a big sign next-door to where the prostitutes are sitting in the cool hallway: "Don't Let Us Reach Three Percent!"