Two Children With the AIDS Virus, Two Ways of Coping With Tragedy : Disease: The little girl has become a public symbol of the danger to youngsters. The boy’s infection is kept secret--even from him.

Four-year-old Stephie knows she’s sick, and she knows it’s because her mother injected drugs. She knows also that she will someday go to Heaven, a beautiful place where angels live.

Tom, 6, knows none of these things. Like Stephie, he is infected with the AIDS virus, but his mother has chosen to keep it a secret from classmates, teachers, neighbors--even from Tom.

“It’s a hush-up thing,” his mother said. “Everyone’s ignorant of the facts.”

After 10 years, the AIDS epidemic’s course among its littlest victims can be seen in the statistics: more than 3,000 cases of AIDS in children under 13 reported to the federal Centers for Disease Control, 2,500 of them under age 5, though officials believe the actual number is much higher.

The story is also told in the lives of Stephie and Tom--the one child whose illness is an open book, who is bathed in attention; the other whose infection is hidden for fear that hard hearts will turn against him and his family.

Stephie’s grandmother, Edie Schaefer, has made AIDS education her cause and Stephie a local celebrity. The cheerful little girl with long blond curls has been on talk shows and in the news since she was less than a year old.

“If I feel we can help one or two other people, then Stephie will not die in vain,” Schaefer said. “That’s what keeps me going.”

Stephie was 11 months old when she was discovered to have AIDS. Her liver and spleen are enlarged and her lymph nodes are swollen and as hard as dried peas.

Stephie’s mother, an intravenous drug user infected with the AIDS virus, left Stephie with relatives and fled to Arizona, where she still lives. Another of Schaefer’s four daughters kept the baby for a few months, but she wanted to work and was unable to find a nursery willing to take an infected child.

The family took their plight to their state senator, and Stephie made the news for the first time. Suitable child care was never found, Schaefer says, so she decided to stay home and take care of Stephie.

The next roadblock came when Edie wanted to have the baby christened: The first two priests she asked never returned her phone calls.

Stephie’s bedroom is full of toys, many of them gifts from strangers. Stuffed animals are displayed in rows around the room and piled on her bed. Games cover the floor, leaving only a narrow pathway to the door.

She likes to play house and one day brought a visiting reporter and photographer into the game. She called them her children and served them small bowls of her specialty, “chocolate soup.”

One of her favorite toys is a child’s tape recorder with a microphone that amplifies her voice when she sings along with songs she knows by heart.

“I can be anything I dream. Here in my own world, it’s only up to me,” she sings, and she smiles.

So what does she want to be?

“A ‘P!’ An ‘M!’ ” she answers, mimicking a cheerleader.

In past years, most children born with HIV died before they were 3, according to Dr. Harold Lischner, chief of immunology at St. Christopher’s Hospital for Children in Philadelphia. Now, he said, most live to see their sixth birthdays. The oldest juvenile patients are entering their teens, thanks to early detection and new treatments toward off infections.

Stephie takes doses of the drug AZT three times a day, and since February she has received monthly infusions of gamma globulin to fight infection. She has fewer colds and does not tire as quickly as she once did, Schaefer said.

She seems healthy, but Schaefer has no illusions.

“We talk about God in Heaven and she knows she’s sick and someday she’ll go to Heaven--and so will I.”

Tom, so far, has no symptoms. His condition was diagnosed when he was 3.

His mother, a former intravenous drug user, learned she had HIV when she was six months pregnant with her second son. She worried about herself and the unborn baby but assumed her older son was fine.

After the baby was born, both children were tested. The younger boy was fine, but Tom was positive.

“I get depressed,” his mother said. “Every time I get sick, I’m afraid I’m going to die. Part of it’s from being a mother. What’s going to happen to the kids after I’m gone?”

Tom attends a public elementary school in Philadelphia. According to the school district’s AIDS policy, in force since 1985, only the superintendent, the district medical director and school nurse need know that a child has the AIDS virus. Tom’s mother informed the principal before he began attending school.

Teachers are taught to don gloves before touching any bleeding child. Blood contact can transmit not only the AIDS virus but also hepatitis and other diseases.

Tom is not the boy’s real name. Out of fear of discrimination, his mother has told only her own mother and the principal of her son’s infection. If his friends knew, “They would put him aside. He’d be an outcast,” she said.

He is not an outcast now. He is a playful, animated boy with closely cropped brown hair. He takes AZT and goes to the hospital for a gamma globulin infusion once a month.

His mother says she does not tell him about his condition because she does not believe he is old enough to understand. But, try as she might, she knows she cannot shield him forever from the truth.

When he asks her, she says, “I hope I find the right words to say.”