The majority of gay men now being diagnosed with AIDS are either black or Hispanic, not white, according to a report released yesterday by the Centers for Disease Control and Prevention.

Black and Hispanic gay men also tend to become infected at a younger age than whites, suggesting that minority teenagers may be especially vulnerable to the AIDS epidemic, or may be uninformed about their risky behavior. In addition, black and Hispanic men who have sex with other men are less likely than whites to call themselves homosexual--a stance that experts say may hinder disease-prevention campaigns in their communities.

The data highlights the dramatic shift in the U.S. AIDS epidemic in the past decade. Originally a disease of middle-class whites, it is now growing most rapidly in communities of color, where especially strong stigmas against homosexuality may be helping to fuel the spread.

As has been true since AIDS was first recognized in 1981, sexual contact between men remains the most common way in which the human immunodeficiency virus (HIV) is transmitted in the United States.

"From our surveillance data . . . it was just a matter of time before this crossover [of racial groups] would occur," said Helene Gayle, director of the CDC's center for HIV prevention, at a news conference in Atlanta. "This trend has been going on all along, and people have ignored it. In a lot of ways, the surprise is that people are surprised."

Racial and ethnic minorities accounted for 52 percent of the AIDS cases diagnosed in gay men in 1998, the last year for which data are complete. It was the first year in which whites did not constitute a majority of the new AIDS cases diagnosed among gays. Ten years earlier, in 1989, minorities made up 31 percent of new cases in gay men.

In gay men "of color" diagnosed with AIDS in 1996, 1997 and 1998, 5 percent were ages 13 through 24, and 14 percent were ages 25 through 29. Among newly infected white gay men, only 2 percent and 9 percent were in those age brackets, respectively, according to the CDC report.

AIDS is the late stage of HIV infection, in which symptoms of severe immune-system damage are present. People diagnosed with AIDS in 1998 actually acquired the infection much earlier, living for 5 to 10 years symptom-free before their diagnosis. Consequently, the 1998 data represent infection trends from early in the decade.

Many states, however, now require that doctors report not only new AIDS cases, but new cases of symptom-free HIV infection as well. Those new-infection statistics, although not available for the whole nation, show trends similar to that for AIDS.

CDC officials also released the results of a survey of 8,780 men who acquired HIV infection from sex with other men. Twenty-four percent of the blacks in the group identified themselves as heterosexuals, as did 15 percent of the Hispanics. In comparison, only 7 percent of whites in the group called themselves heterosexuals.

Men who become infected from homosexual contact, but don't acknowledge their behavior to themselves or others, may be passing the disease to female partners who are unaware of their high risk, Gayle said.

"Fear remains a powerful force in communities of color," she added. "Fear drives too many gay and bisexual men of color to die alone rather than reveal that they are gay. . . . Fear drives too many families, when they learn that a son has AIDS, to hope that he is a drug user rather than that he is a homosexual."

Phill Wilson, director of the African-American AIDS Policy & Training Institute at the University of Southern California, said he rejects the notion that homosexuality is more stigmatized in the black community than in the white. However, he thinks the stigma among blacks, when it occurs, can be more devastating.

"The role of the [black] church has been to provide sanctuary," he said. If a congregation rejects a member who is gay and has AIDS, "whole families can lose their sense of sanctuary. I am not the only one who is impacted. My mother . . . my aunt . . . our whole families are affected."

Rafael Campo, a gay Hispanic physician from Harvard Medical School, said that the Roman Catholic Church is similarly central to many Hispanic communities, and its opposition to homosexuality and condom use may "put them at higher risk for HIV and AIDS."

Campo also said that many prominent Hispanic Americans have been reluctant to speak out on behalf of AIDS prevention. He and some Harvard colleagues convened a meeting of Hispanic leaders in May 1998 to enlist their support for a campaign called "Leading for Life."

"Quite sadly, none of the prominent Latinos with the exception of [Puerto Rican actress] Rosie Perez came to he summit," he said. "We had invited elected officials, prominent sports figures, entertainment leaders. It was kind of astonishing to see the silence in action."

The number of AIDS cases and AIDS deaths has been declining for only a few years, but the risk and demographic profile of the epidemic has been evolving for more than a decade.

In 1985, 66 percent of new AIDS cases occurred through male homosexual sex, 17 percent through intravenous drug use and 2 percent through heterosexual sex. In 1998, 41 percent were acquired through homosexual sex, 29 percent through drug use and 23 percent through heterosexual contact. In 1985, 40 percent of newly diagnosed AIDS patients were black or Hispanic. In 1998, 68 percent were.