In a study of HIV/AIDS data from 32 states, the Centers for Disease Control and Prevention (news - web sites) said 11 percent more infections were diagnosed from 2000 through 2003 among men who have sex with men. The study was released to commemorate World AIDS Day.

Gay and bisexual males accounted for 44 percent of the 125,800 diagnoses reported by these states during the period, the Atlanta-based agency said.

"This is not a trend we want to ignore," said Dr. Ronald Valdiserri, deputy director of the CDC's HIV/AIDS prevention program. "We need to make sure the leadership in the gay community understands the importance of tracking this very carefully.

The HIV/AIDS diagnosis rate for the overall population remained relatively stable at 19.7 cases per 100,000 people in 2003, compared to 19.5 per 100,000 people in 2000, the CDC said. Blacks, who represent about 13 percent of the U.S. population, made up 51 percent of all diagnoses from 2000 to 2003.

Valdiserri said the findings appeared to back up other studies that suggested rising HIV infections among gay and bisexual males, but he added that the limited geographical reach of the study made it difficult to determine the exact scope of the epidemic.

New York, California and 16 other states which had not met reporting standards were excluded from the study.

AIDS, which destroys the immune system and leaves victims vulnerable to an array of opportunistic infections and cancers, has killed about half a million Americans and 22 million people worldwide since 1981.

U.S. public-health experts have been warning of a possible resurgence of the epidemic, which eased in the early 1990s following the development of antiretroviral drugs targeting the disease.

Since the late 1990s, when U.S. deaths from AIDS stabilized at 16,000 per year and new HIV infections stabilized at 40,000 per year, the disease has shown signs of a comeback, particularly among gay and bisexual men.

This group is believed to account for a majority of the estimated 850,000 to 950,000 Americans living with HIV, the virus that causes the disease.

A recent surge in syphilis infections among gay and bisexual men has prompted concern among infectious disease experts and public health officials. Syphilis and other sexually transmitted diseases increase the risk of contracting HIV.

To combat the changing scope of the AIDS epidemic in America, the U.S. government decided last year to emphasize programs that focus on testing and counseling people who are already infected.

Some AIDS activists have attacked the new approach, saying it will lead to reduced funding for many programs that emphasize condom use and other safe-sex practices for uninfected people.

The CDC also has recommended routine HIV testing be expanded to include pregnant women, intravenous-drug users and anyone who engages in unsafe sex.