The message for young people, she said, is don’t pig out on sex.

Shirley Fanin, Los Angeles County’s director of communicable disease control, joined the parents’ council at Patrick Henry Junior High School in Granada Hills this week to talk about AIDS.

That topic was apparently a little more sexy to the media than to most of the parents of Granada Hills.

An audience of only about 50, among them two television news crews and myself, assembled in the school library Monday evening under computer-printed signs that said things like “Pig Out on Books.” Another 50 seats were empty.

The television people ran wires across the floor, raised lights on tall tripods and taped microphones to a small wooden lectern that was set on top of a library table, fitting over a portable loud speaker.

Fanin, a small, full, graying woman wearing a navy blue, dotted Swiss dress, almost vanished behind the lectern. But she had a lot of presence.

She began slowly and precisely, giving an outline of the medical detective story behind the discovery of the deadly acquired immune deficiency syndrome in Los Angeles County a few years ago. The story was compelling, at least partly because Fanin herself was one of its primary characters.

It was tough going, however. The narrative was frequently punctuated by long Latin terms, and it rested largely on statistical theory that obviously was clearer to Fanin than to most of those in the audience.

It wasn’t making good film.

Within half an hour, the cameramen were rustling.

A young man in a football jacket scooted in front of Fanin, low like an Indian, to retrieve his wires and lights. When everything else was in order, he crawled up to the lectern and reached up to rip away the duct tape that held his microphone in place.

Unfazed, Fanin talked on.

Both TV crews had long rattled out when Fanin got to the good part, giving her views on homosexual bathhouses, children with AIDS in school and the possibility that clean, straight people, like those in the audience seemed to be, might contract AIDS by unwittingly touching someone who has it.

Mostly her message wasn’t about science and medicine. It was about fear.

Public fear, she said, is the worst possible defense against AIDS.

She reassured a sometimes skeptical audience that children do not get AIDS in school, adults do not get it in public and, although homosexuals do get it in bathhouses, closing homosexual bathhouses is not the answer, either.

A parent’s best AIDS prevention tool is education, she said.

The message for young people, essentially, she said, is don’t pig out on sex.

“I think we have to start teaching our children that it’s not let it all hang out anymore,” Fanin said. “It is time to say, ‘I must choose to select and choose whether I am going to become sexually active, with whom, and just how much risk I’m willing to take. . . .’ The sexually promiscuous teen-ager in a population where the virus is circulating is going to be high-risk herself. So we need to be forthright and straight out with that teen-ager. And we need to cut out the euphemisms.”

With chilling logic, Fanin dismissed the much-held notion that AIDS can be successfully quarantined or isolated.

“In a place like Los Angeles and San Francisco and New York City, it’s highly unlikely, unless you’ve been living very isolated, that you have not had casual contact with somebody who’s already had this viral infection,” she said. “If this were a casually transmitted disease, then most likely most of us would already have been exposed.”

Fanin pleaded with her audience to believe that AIDS cannot be spread in public.

“Some people say, ‘Ah, what if a person with AIDS were in the pool and they cut their foot and they bled and I sat down and I and had a cut where I sat down?’ ” she said. “When was the last time you sat in somebody’s blood? How do you answer these things? It’s like saying, ‘What if the cook in the restaurant had AIDS and they cut their hand and bled on my salad?’ When’s the last time you ate bloody salad? Let’s be real, people.”

Still, some in the audience weren’t totally soothed.

When Fanin asked for questions, a white-haired man raised the argument that, because certain unorthodox behaviors are linked to the spread of hepatitis B as well as AIDS, maybe it was time to consider a “two-edged sword” approach.

That displeased Fanin, who read into the remark an attack on homosexuality.

“Any heterosexuality or homosexuality, if it practices the same type of behaviors, is a high-risk group,” she said. “But to say only homosexuals is begging the issue. You’re really focusing on a scapegoat. A man who goes to prostitutes frequently and consistently is also at a risk of taking the disease home to his family.”

“I’m not condoning that practice, either,” the man said, not conceding the point.

“That’s why I’m saying we have to change our attitude,” Fanin said.

“That’s what I’m saying, too,” the man said.

“But we don’t do it by picking scapegoats,” she said. “We have to do it by understanding. . . . Nobody asks to get AIDS, and nobody should be accused of doing something deliberately to get it or give it to somebody else.”

On that note she ended and the audience left. It wasn’t clear whether, deep in their hearts, they felt safer or not.