They still don't know how it happened.
A decade ago, Kimberly Bergalis stepped forward to announce that she had AIDS. The pretty Floridian had none of the known risk factors for the disease; she had not had sex, she did not share needles, she had not had blood transfusions.
But she had gone to a dentist to have two teeth pulled, and somehow he gave her AIDS.
It was the first documented case of AIDS transmission from a health care professional to a patient, stunning the public and confounding the experts.
There were efforts to make AIDS testing mandatory and other attempts to force infected doctors to reveal their disease; in 1991 the government issued guidelines designed to protect patients from HIV-infected health workers.
"It really created a whole aura of suspicion of health care providers that hadn't existed before--the perception that your health care provider could be dangerous to your health," said Dr. Kenneth Mayer, director of a Brown University AIDS program.
Ultimately, health officials traced AIDS infections in five other patients to the same dentist, Dr. David Acer; he died four days before Kimberly Bergalis went public. For the last 15 months of her life, she pleaded for mandatory testing of health care workers and patients before invasive procedures.
The AIDS landscape has changed dramatically since Bergalis sat back in Acer's dental chair in December 1987. Powerful drugs have been developed that make AIDS less virulent, and the number of new AIDS cases reported nationwide each year has stabilized.
U.S. Centers for Disease Control and Prevention guidelines still recommend barring HIV-infected doctors from performing certain invasive procedures without patient consent and approval from an expert review panel.
But the CDC--urged on by groups ranging from gay activists to the American Medical Assn.--is thinking about loosening those rules. Because nearly a decade later, the Acer cases remain the only known instances of clinician-to-patient AIDS transmission nationwide.
Some experts said that shows how tiny the risks are. Others said they illustrate the success of increased infection control practices prompted by Acer's trail of misery.
But to this day, no one can say just how Acer infected his patients with the deadly virus.
It is a mystery that most AIDS experts acknowledge may never be solved.
Now 44 and living in the lakeside town of Empire, Mich., Lisa Shoemaker is one of two survivors among the patients Acer infected. There are two reasons she is still alive, she said: luck and medical advances.
Her disease has remained relatively dormant. Each day, she takes 14 pills, including a protease inhibitor that wasn't available until 1997. Combined with other anti-AIDS drugs, it can bolster the immune system and reduce the level of virus in the blood to undetectable levels.
In 1988 she was suffering from two abscessed teeth. She was new to Stuart, Fla., and didn't have a dentist; she picked Acer on the basis of the "painless dentist" promotional magnet she had received from a welcome wagon-type group.
"I went in very naive and very trusting. I'm not like that anymore," she said.
Her memories of that office visit are still vivid. Acer "was wearing gloves and a mask," she recalled. "He was very skeletal-looking. I thought he had cancer." She never suspected AIDS.
Her face swelled from the Novocain, but Shoemaker said the visit was otherwise routine.
When she had an AIDS test the next year, it had nothing to do with her visit to the dentist; she suspected that her fiance had engaged in unsafe sex. And when the result was positive, it was a thunderclap. She blamed her boyfriend.
The couple split up, and Shoemaker moved home to Michigan. It was only in 1990 that she learned the real source of her infection, after her father saw an article about Acer.
She became an activist. She went to schools to speak about the disease. She testified before Congress, supporting measures to force HIV-infected patients to reveal their disease to their sexual partners, and urging that AIDS testing become mandatory for doctors and part of yearly routine checkups for others.
Shoemaker and Sherry Johnson, the other survivor among those infected by Acer, oppose relaxing the CDC guidelines. Infected health care workers should not hide their disease from patients, they said.
"You're kind of putting your life into their hands," said Johnson. She is 25 now; she was about 11 when Acer filled her cavities.
Both women feel a moral obligation to tell doctors that they are infected.
"To me, not revealing my status would be like holding up a revolver to their heads with one bullet and spinning it, playing Russian roulette," Shoemaker told Congress in 1998. "Those who are uninfected need to be given their rights back."
That the risks of doctor-to-patient transmission are so slim is small consolation.
"They'll always say it only happened once," Shoemaker said. "Well, it's like six people were in that 'once.' "