The fear is very real despite two reassuring facts:
* There apparently has been no confirmed case of AIDS being passed on to a child during a sexual attack.
* Some experts believe that the chance of transmission under such circumstances is relatively slim.
But, said Dr. Stephen Ludwig, director of emergency medicine at Children's Hospital of Philadelphia, "we are, I think, all feeling that it's only a matter of time."
It appeared that the time had come this month when authorities in Texas revealed that a man who had sexually abused at least 25 boys was thought to have had AIDS.
The chilling news came after Jimmy Glenn Etheridge, 38, an insurance salesman in the town of Marlin, was shot to death by a 16-year-old boy who shared his home.
When authorities said that initial tests indicated that Etheridge had carried the AIDS virus, a wave of fear swept through the town of 6,000 residents.
The fear abated when health officials determined that the early blood test had been wrong, but the incident served to underscore concern among child- health experts and parents who say they have worried for years that AIDS will be transmitted by sex offenders.
And although there is no evidence to date that AIDS has been transmitted by a child molester, investigators in California last week disclosed that several cases of another sexually transmitted disease have been found among children who attend a day-care center that is under investigation for alleged child abuse.
Authorities said that 85 children enrolled at the Presidio Child Development Center on the Army base at Presidio have been examined in the wake of child-abuse allegations.
"Several" of the children were found to be infected with chlamydia, the most common sexually transmitted disease in the United States. A bacterium that attacks the mucous membranes, it can cause blindness if left untreated.
Charges of child molestation against a worker at the center were dismissed earlier this year when testimony from the victim's family and physician was barred as hearsay in federal court. Authorities said they were still investigating complaints of abuse at the center.
Nationwide, about 250,000 cases of child sexual abuse are reported each year, according to the National Committee for Prevention of Child Abuse. The number of young victims who come in contact with AIDS carriers is impossible to estimate, but some experts who study the behavior of molesters say that the chance of this happening may be small.
"The risk is not that great," said David Finkelhor, one of the nation's foremost researchers on child sexual abuse. "My guess is that the risk to an adolescent child who has unprotected sex with peers is probably as great as for a child who would be molested."
Margaret Oxtoby, a researcher at the federal Centers for Disease Control, said there was no evidence that any of the 562 children under 13 who have AIDS were infected by a child molester, "but it certainly is a (possible) mode of transmission."
Other experts point out that although most molesters do not belong to two of the highest-risk groups - homosexuals or intravenous-drug users - other factors may make them more likely to come in contact with AIDS.
ISSUE OF PROMISCUITY
One of those factors is promiscuity. New research from psychiatrist Gene G. Abel of Emory University in Atlanta suggests that child molesters may have sex with an enormous number of children.
Abel's ongoing study of 550 male molesters found that this relatively small group accounted for 65,000 acts of child sexual abuse; the molesters who favored girls averaged 30 to 50 victims each; those who favored boys had averaged 200 victims.
Abel also found that child molesters who were attracted exclusively to children were rare. About 85 percent of the group he studied had sex with both children and adults - which meant that they were more likely to come in contact with AIDS than those who associated strictly with children. Most of those adult sexual contacts, however, were with women, who generally are at a much lower risk of carrying AIDS, Abel said.
Another factor increasing the AIDS threat for young abuse victims is that, unlike consenting adults, they are usually completely under the control of those who molest them.
"Children, when they are molested, don't even have a prayer of exercising safe sex," said Ann Cohn, executive director of the National Committee for Prevention of Child Abuse.
Fortunately, said researcher Finkelhor, child molesters often do not
sexually penetrate their young victims, which would considerably increase the risk of AIDS transmission. In many cases, he said, the sexual relationships with youngsters "are more like a game" involving masturbation and sexual fondling.
Finkelhor and many other experts agree that most child molesters are not strangers to the children they attack and, in fact, are often relatives.
It is also widely agreed that most child molesters are not homosexual and do not associate with the gay community - the group at highest risk in America for contracting acquired immune deficiency syndrome.
Even males who molest male children - sometimes called homosexual pedophiles - "are not interested in adult male partners," Finkelhor said. ''Many, if they have any sexual relationships (with adults), will have a kind of marriage which covers their actual sexual preference, which is for children."
He added, however, that the situation "is a little bit different" with men who have a sexual interest in teenage boys. These men, Finkelhor said, are more likely to have adult homosexual contacts - just as heterosexual males who are attracted to teenage girls might also have contacts with adult women.
Figures from the CDC suggest that there may be an AIDS link between adult homosexual men and teenagers.
Although most of the 562 children in the United States under age 13 who have AIDS contracted the disease in the womb from infected parents or from blood transfusions, a majority of the 130 teenage boys 13 through 19 who have AIDS apparently contracted the virus during homosexual contact.
The belief among experts that some young abuse victims will begin contracting AIDS has produced a new medical dilemma: Is it best to begin routinely testing abused children for presence of the fatal virus or will the tests themselves cause unnecessary anguish and fear?
At Mount Sinai Medical Center in Chicago, which treats about 600 young sex- abuse victims a year, medical staffers "are very seriously looking" at an AIDS test, said Howard Levy, head of the hospital's child-abuse unit.
It would be added to the panel of tests routinely administered to abused children to find out if they have contracted sexually transmitted diseases such as gonorrhea or syphilis.
An AIDS test could "create stress in the parents and potentially in the child," Levy said.
Yet, if children are not tested for exposure to the virus, Levy said, "I would have a real problem morally down the line when a group of kids I should have tested later develops symptoms of the disease, and two or three years later (researchers) develop something that might have helped them."
But other experts are reluctant to give AIDS tests, and some are actually arguing that this may be one area in which ignorance of the disease's presence is best.
"Ask yourself the question - what is the advantage of knowing your child has been exposed to AIDS?" said Cohn of the National Committee for Prevention of Child Abuse.
Even if a blood test showed that a child had been exposed to the disease, ''you basically wait five or seven years to see if the child will develop the (AIDS) symptoms," Cohn said.