In a sign of progress against one of the great plagues of the last generation, a dwindling number of New York City AIDS cases has been diagnosed over the last eight years, according to new statistics released on Friday.

The number of adults with newly diagnosed AIDS dropped to 2,225 in the 2011 fiscal year, which ended on June 30. That total was 25 percent lower than the total for the year before (2,969 new diagnoses), 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 on Friday.

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