While just a teenager in the 1970s, she danced on The Block, where she snorted cocaine and heroin and sold sex in backrooms. Later, with her addictions firmly rooted, she set out on her own, offering her body on the streets of West Baltimore as a deadly virus was spreading.

The years have worn away at Sharon Williams, whose deeply lined face, reddened eyes and pained expressions tell of poor health, nights in abandoned buildings and customers like the man who kicked her down a flight of stairs, breaking two ribs and puncturing a lung.Yet she remained a prostitute to support herself and her habits. Not even the discovery 12 years ago that she had been infected with HIV changed that. She also counts herself among the many addicted women who, despite knowing the risks, have given in to customers who refuse to wear condoms.

"They'll do anything for a high," Williams said. "If they want money enough, they'll agree to it. I've slipped up once in a while."

The sale of sex for drug money is an important but largely overlooked reason why Baltimore has the nation's second-highest rate of AIDS diagnoses, trailing only Miami. By the end of last year, almost 16,000 city residents were living with HIV or AIDS.

Women desperate for their next fix and men willing to risk their health for cheap sex are partners in an epidemic that shows no signs of ending. Experts consider prostitutes to be "core transmitters" because of their high infection rates and large numbers of partners.

Therapeutic advances have prolonged life while education has lowered the overall HIV infection rate. Still, the death toll from AIDS continues to mount, reaching almost 9,800 in Baltimore since the epidemic began in the early 1980s. The disease has devastated families, leaving children without parents and often killing multiple relatives. It is the leading cause of death among adults 35 to 44 years of age, surpassing homicide, and has had a corrosive effect on neighborhoods already beset by poverty, crime and homelessness.

At last count, Baltimore's rate of new AIDS diagnoses was nearly three times the nation's, 21 percent higher than New York's and almost double San Francisco's - two cities that people more commonly associate with the epidemic.

In certain parts of the city, the impact is even more striking. In ZIP code 21217, which includes Sandtown-Winchester and the Pennsylvania Avenue corridor, the percentage of people living with HIV/AIDS is 15 times the national average.

Public health authorities have been slow to address the connection between AIDS and what some experts call "survival sex," in part because the people involved are elusive and their role hard to quantify. Most of the women have been addicted to drugs and, in some cases, ensnared in prostitution since childhood. Many are homeless, wandering from one abandoned building to another.

The prevalence of crack

A key part of the sex trade, epidemiologists say, is crack cocaine. The drug produces an intense high followed quickly by a crushing depression that can be relieved only by smoking more. Crack, which has been a major presence in Baltimore since the early 1990s, drives many female addicts into a relentless cycle of drug-seeking and prostitution.

"They have a lot of partners to sustain their habits," said Dr. Jacques Normand, chief of the AIDS program at the National Institute on Drug Abuse. "There is no question in this country that there's a substantial epidemiological relationship between crack and HIV transmission. It all comes down to the trading of sex and drugs."

Terry Brown, vice president of Baltimore Behavioral Health, daily sees the link between drug use and prostitution among the women who enter his drug treatment center. "I would say that if we have a woman who is a substance abuser, is unemployed and has no income, the way she supports her habit is the sex trade," said Brown, who is co-chairman of the city's Commission on HIV/AIDS Prevention and Treatment.

In a months-long examination, The Sun interviewed physicians, advocates, social workers, addiction counselors and public health experts to learn how the sex trade contributes to the greater epidemic. The best understanding, however, comes from the stories shared by nearly 20 women who have fed their addictions this way.

Many of the women were initiated into prostitution around puberty. Several told of childhoods in which fathers or relatives forced them to have sex with men to support their own drug habits. Soon the girls were getting high to numb their shame.

As women selling sex for drugs, many have been routinely exposed to beatings, robberies and sexually transmitted diseases, including HIV.

"They're holding on for dear life," said Sidney Ford, who runs a drop-in center on West Pratt Street called You Are Never Alone. "They feel they're doing all they can to keep that grasp on what little bit of life they see is left for them."

In Baltimore, the neighborhoods most afflicted by HIV/AIDS flank downtown, sweeping past Johns Hopkins Hospital on the east and curving from Druid Hill Park past Carroll Park on the west. They are the same ones heavy with drug dealers, jobless residents and prostitutes.

About dusk one day, a stream of young people traipsed north from Pigtown to Sandtown in search of drugs. Hours later, their purchases completed, they hurried home along streets where prostitutes struck solitary poses. The women wore blank expressions and shabby clothes as they awaited passers-by and motorists.