ATLANTA (AP) — The number of newly diagnosed cases of HIV among gay and bisexual men rose in 2002 for the third straight year — a disturbing turnaround from the 1990s that health officials say reflects growing complacency about the dangers of AIDS.

“If we let down our guard even a little bit this is the kind of thing that can happen,” said Dr. Ronald Valdiserri, a CDC deputy director.

HIV diagnoses among gay and bisexual men rose 7.1 percent in 2002 in 25 states with long-standing HIV reporting procedures, the Centers for Disease Control and Prevention said. The number represented an increase of nearly 18 percent since 1999.

That is disturbing, because the number of newly diagnosed HIV cases per year fell steadily throughout the 1990s, even among gay men.

The increase in HIV cases can be blamed on a younger generation that does not remember the devastation of the AIDS epidemic, lack of concern because of the advent of life-extending AIDS-treatment drugs and burnout from years of safe-sex warnings, health officials have said.

“We continue to sound this warning note to communities and state and local health departments that we need to redouble our efforts,” Valdiserri said.

New cases also continue to rise because people are not diagnosed early enough and pass the infection to others before they know they have HIV, the CDC said. Officials also said it is difficult for people to adhere to complex HIV drug regimens.

The CDC reported 42,136 AIDS diagnoses in the United States last year, a 2.2 increase from the previous year. There were 16,371 AIDS deaths in 2002 — a 5.9 percent decline from 2001.

The statistics highlight the need for more prevention efforts aimed at gay and bisexual men, said David Ernesto Munar of the AIDS Foundation of Chicago.

The CDC plans to provide money to community groups in large cities that have had outbreaks of sexually transmitted diseases, such as syphilis and AIDS, Valdiserri said.

The report on HIV among gays and bisexuals does not include New York, California or Florida — areas of high HIV activity in the past. Also, the report does not indicate whether the new diagnoses are new or old infections; CDC officials recently unveiled a system that will be able to detect new infections starting in 2004.