Young gay men are contracting the AIDS virus at a rate not seen in more than a decade, federal health officials reported yesterday.

Unveiled less than a week before the 20th anniversary of the first published description of AIDS, the new data suggest there may be a "resurgent epidemic" among gay men, the population in which the disease was originally found. Particularly troubling are the findings for young gay black men, whose annual rate of new infection is three times that of young gay men overall.

The data underscore "the need to reach each generation of gay and bisexual men early -- and to sustain those efforts as they age," Helene Gayle, head of AIDS prevention programs at the federal Centers for Disease Control and Prevention, said at a news conference.

A survey of 2,942 gay men ages 23 to 29 conducted in six cities from 1998 to 2000 found that 4.4 percent were becoming infected with the human immunodeficiency virus each year. The pace of new infections, called the "incidence rate," varied greatly by race and ethnicity. It was 2.5 percent among whites, 3.5 percent among Hispanics and 14.7 percent among blacks.

The survey showed that 32 percent of young black gays were already infected, as were 14 percent of Hispanics and 7 percent of whites. That prevalence will rise if the pace of infections continues unchanged.

"I'm very concerned about the pockets of epidemic that we are seeing," Surgeon General David Satcher said. "Thirty percent -- that's approaching Botswana's level of infection."

Reasons for the increase are unknown. Some experts believe the spectacular improvement in treatment in the past five years has led many young people to view HIV infection as a manageable, chronic disease. Others believe the main reason is generational: Young gays have no memory of the terror-filled early days of the AIDS epidemic and little contact with people who do.

Phill Wilson, founder of the African American AIDS Policy and Training Institute, an activist organization in Los Angeles, said the data show "we have a screaming emergency . . . and that we've failed in developing prevention messages for young black men who have sex with men."

He said he believes the country has been reluctant to produce prevention campaigns aimed at gay black men. A broad social prejudice against young black men, which leads to low self-esteem among them, is also contributing to the high infection rate, he said.

"We cannot ask someone to protect his life if you have not convinced him that his life is worth protecting," Wilson said.

The CDC provides about $400 million for state and local AIDS prevention programs that target high-risk groups. This year, the agency is also providing $15 million for the development of prevention campaigns by and for gay black men.

The study released yesterday surveyed young gay men at shopping areas, dance clubs, bars and community organizations in Baltimore, Dallas, Los Angeles, Miami, New York and Seattle. Because the population and research methods differ from previous studies, it's impossible to say precisely how much the incidence rate has increased. It appears, however, that after a long downward trend, the epidemic in young gay men is clearly on the upswing.

At the time a syndrome of severe immune deficiency in gay men was first recognized in Los Angeles in early 1981, the HIV incidence in that population was about 20 percent a year. That is known because after a blood test for AIDS was developed in 1985, researchers went back and looked for the virus in samples of blood given periodically in the late 1970s by gay men in a study of the hepatitis B vaccine.

In 1983, when the sexual transmission was known and campaigns for "safer sex" had begun, incidence in a study of gay men was 18 percent. Between 1985 and 1990, it had fallen to 3 percent to 5 percent, as revealed by about 10 studies done in various cities and age groups, said Linda Valleroy, a CDC epidemiologist who headed the recent study.

By the 1990s, a variety of studies showed annual new infection rates of 1.6 percent to 3.5 percent, she said. The latest incidence is higher than that: 4.4 percent.

An incidence of 14.7 percent -- the rate seen in young black gays -- leads rapidly to a state where the majority of that population is infected. This is demonstrated by a mathematical projection done recently by Robert Janssen, a CDC epidemiologist.

Start with a population of 22-year-olds in which 20 percent are infected with HIV. With a 14 percent annual incidence of infection, 70 percent of the group will have the infection by the time they are 29.

It's not known whether the HIV incidence for the U.S. population as a whole is rising or falling, although there are studies planned to determine that, Gayle said.

Since 1981, more than 1 million Americans have been infected with the virus, and about 450,000 have died.

About 323,000 people are living with AIDS, which is the stage of the infection when the virus has caused significant damage to the immune system, CDC officials said. The number of people reaching that stage peaked in the mid-1990s and has declined steadily since then, as effective antiviral therapy has allowed thousands of patients to slow or stop the damage caused by HIV.

The AIDS era formally began with a description of five homosexual men from Los Angeles who had Pneumocystis carinii pneumonia, an infection seen nearly exclusively in people with damaged immune systems. It appeared in the CDC's newsletter Morbidity and Mortality Weekly Report on June 5, 1981.