Vy and Chenda say they are 23 years old, and Likay, just 19, but they all look much younger. All three work as prostitutes, entertaining three or four clients daily in their cramped wooden boarding house for about 5,000 Cambodian riel per "trick" -- less than $2.

All three women have heard of the human immunodeficiency virus (HIV), and they all say they use condoms, called "Number One" here after the most common brand. But, Chenda says, "The men don't like to use condoms," and she admits having had unprotected sex "one or two times for big money." For her, "big money" is $15, paid in dollars.

The three women and the thousands more like them in the teeming dirt alleyways and in the bars and brothels of Phnom Penh are at the forefront of what health care professionals warn is an emerging AIDS catastrophe unlike any seen outside of sub-Saharan Africa. Tiny Cambodia, ravaged by civil war and the genocide of the Khmer Rouge era, damaged by American bombs and embroiled in a long-running guerrilla war, is now set for a new and more insidious type of destruction -- from a virus that now infects between 1.6 and 2 percent of the adult population and could reach 2.3 percent by 2000.

Cambodia has already surpassed Thailand as Asia's most infected country, and in less than half the time it took Thailand to get there. The numbers are staggering. The rate of HIV in pregnant women is about 2.6 percent. One of every 10 university students is infected; nearly one in four soldiers carries the HIV virus. The World Health Organization has said Cambodia can expect 12,000 new AIDS patients this year and next, for a total of 40,000 by the turn of the century.

Moreover, between 40 and 45 percent of all prostitutes, like the three women at the boarding house, are believed to be infected, and many continue working even after being diagnosed. Yves Marchandy, the mission chief at a hospital run by the aid group Doctors Without Borders, tells of a prostitute hospitalized with AIDS who continued having sex with customers from her sickbed until the day she died; she needed the 5,000 riel per day to pay for her hospitalization.

"The increasing rate in Cambodia makes it the fastest in the world," Marchandy said. "In two years, we'll have 40,000 people with AIDS -- and there are only 10 million people in this country. If you compare that with Thailand, it's a disaster."

"In Cambodia, the problem is of African proportions," said Kul C. Gautam, East Asia regional director of the United Nations Children's Fund in Bangkok. "It's like Malawi, where huge percentages are infected. And in Cambodia, the government is not doing anything -- they are too busy fighting each other. There is also a decay in social values taking place."

Unlike neighboring Thailand, where an aggressive $100 million campaign has stemmed the HIV tide, health care in Cambodia is abysmal; the national health budget is just $18 million. And in a country still dealing with the lingering effects of a quarter century of near continuous warfare, a disease like AIDS hardly seems a top priority.

"They have so many worries; why should they worry about AIDS," said Marie Cammal, a French aid worker who helps rescue girls from the streets. "Everything here is a priority."

The disease is spreading rapidly for many reasons: a highly mobile wartime population, porous borders, a high prevalence of other sexually transmitted diseases. But health officials say all the causes essentially boil down to two -- ignorance and poverty. "Ignorance, because they think it comes from mosquitoes,," said Marchandy. "And poverty because of all the problems with prostitutes."

Many here trace Cambodia's flourishing sex industry to the early 1990s, when tens of thousands of U. N. "blue helmet" peacekeepers and civilian administrators descended here in an operation known as UNTAC (U.N. Transitional Authority in Cambodia), which was designed to end a long-running civil war and pave the way for multiparty elections. On election day last month, when Prime Minister Hun Sen was asked what would be UNTAC's legacy, he replied: "AIDS."

Others tend to agree.

"It's a fact that the money that came with UNTAC became a big opportunity for this type of disease," said Marchandy. "For 4,000 years, behind each army is a brothel. It will never change. It's normal."

Now, the effect of the sex culture on Cambodian society is ubiquitous, from the karaoke bars and massage parlors to the open-air restaurants and the Martini disco, where prostitutes -- including girls as young as 10 -- flock around potential clients. "Everywhere there is a brothel. Everywhere there is a massage parlor. It's like Thailand 20 years ago. But AIDS has developed far more quickly here because they don't have the health-care system," said Cammal, who runs a small foundation assisting girls and women who want to leave prostitution behind.

Interviews with prostitutes in Phnom Penh show the extent of the problem.

Likay, the 19-year-old, came here from Prey Veng province after her parents died. Through a friend, she found her way to a small dirt-floor boarding house where the cubicle-size rooms are separated by thin wooden panels.

Likay works as a "beer promoter," going to the outdoor, riverside restaurants wearing a dress and sash with the name of the beer she is paid to promote. There are some 5,000 "beer girls" in the capital, and most, if not all, are thought to have sex with clients for cash.

"I don't like this job," said Likay. "But I have to earn money for food. . . . I'm afraid. Diseases can enter my body." But she takes precautions. She gets a checkup twice a month; she always uses condoms; and she generally stays away from foreigners, who, she believes, are the main carriers of AIDS and other diseases. "For $15, even for $20 -- it's still not enough to catch a disease," she said, through an interpreter.

Likay knows some girls who have become infected with the virus. But, she said, "they still continue to work as prostitutes."

"There's many who know they have it," said Maurits Van Pelt, the Doctors Without Borders mission chief in Cambodia. "They have no choice. They cannot read. They cannot write. This is the only thing they can do."

Vy is another resident of the boarding house. The walls of her cubicle are decorated with newspaper pages and magazine photographs of local models. Her bed is a hard, flowered mattress on a wooden frame, balanced on four bricks. The only light is from a dim red bulb, and an electric fan stirs the hot, sticky air.

"I use a condom every time," Vy says. "If they don't use a condom, I won't sleep with them." And she, too, tries to stay away from foreigners. But, she says, she would take a foreign client for a higher fee -- about $5.

Visiting prostitutes is a common and accepted male pastime in Cambodia.

One result of the brothel culture, said Marchandy, is that in Cambodia AIDS is spread primarily through heterosexual contact. "The men are the vector of the disease," he said. "He goes to the brothel. He has many prostitutes."

Trying to stem the emerging crisis means changing attitudes and behavior -- something that aid workers and health professionals concede is difficult. Some aid groups hand out free condoms to prostitutes, and a random sampling suggests a new awareness of safe sex on the part of the bar girls and beer girls.

But in a country still feeling the effects of land mines, still treating the victims of civil war and Khmer Rouge genocide, and where malaria, tuberculosis and cholera are seen as more immediate threats, AIDS awareness is often lacking.

"It's not a priority here for the moment," Marchandy said. "They need stability first." AIDS Deaths Around The World 1997 estimates among adults aged 15-49 Americas AIDS deaths: 130,000 Rate per 100,000 adult population: 31 HIV/AIDS cases: 2,500,000 Rate per 100,000 adult population: 604 Europe AIDS deaths: 15,000 Rate per 100,000 adult population: 3 HIV/AIDS cases: 680,000 Rate per 100,000 adult population: 153 Africa AIDS deaths: 1,800,000 Rate per 100,000 adult population: 646 HIV/AIDS cases: 20,800,000 Rate per 100,000 adult population: 7,463 Eastern Mediterranean AIDS deaths: 20,000 Rate per 100,000 adult population: 9 HIV/AIDS cases: 310,000 Rate per 100,000 adult population: 136 Southeast Asia AIDS deaths: 230,000 Rate per 100,000 adult population: 30 HIV/AIDS cases: 5,600,000 Rate per 100,000 adult population: 737 Western Pacific AIDS deaths: 18,000 Rate per 100,000 adult population: 2 HIV/AIDS cases: 750,000 Rate per 100,000 adult population: 83 All WHO Member States AIDS deaths: 2,300,000 Rate per 100,000 adult population: 76 HIV/AIDS cases: 30,600,000 Rate per 100,000 adult population: 1,009 SOURCE: World Health Organization CAPTION: Cambodian prostitutes, like these in a brothel area of Phnom Penh, are in the forefront of an emerging AIDS crisis. They have access to little health care. CAPTION: Prostitutes put on makeup and prepare for a night's work in Phnom Penh.