Decreasing age at infection for homosexually acquired HIV in Italy: results of a back-calculation analysis.

The age-specific incidence of homosexually acquired HIV in Italy was examined, based on 3918 AIDS cases diagnosed by the end of 1994 and reported by the end of 1995 through the national surveillance system. Using a smoothed back-calculation analysis, the estimated median age at infection decreased over time, and HIV incidence among younger age groups peaked much later than among older age groups. These results support recent findings from other developed countries, and suggest that measures for preventing homosexual transmission of HIV are best targeted at younger age groups.