The number of adults newly diagnosed with AIDS dropped to 2,225 in the 2011 fiscal year, which ended June 30. That total was 25 percent lower than the total the year before (2,969 cases diagnosed), and 47 percent lower than in the 2003 fiscal year, when there were 4,164 new cases, according to the Mayor’s Management Report, which was released Friday.

Dr. Monica Sweeney, assistant commissioner of the Bureau of H.I.V. Prevention and Control in the city’s Department of Health and Mental Hygiene, said the decline was a “proxy for improved care.”

“It’s not that people are not infected” with H.I.V., the virus that causes AIDS, she said. “It is that they are taking medications, they’re able to be more adherent, treatment has become easier.”