Reconstruction of human immunodeficiency virus (HIV) sub-epidemics in Italian regions.

Abstract

The spread of human immunodeficiency virus (HIV) infections is likely to consist of sub-epidemics in local areas and/or risk groups. Small-area risk group specific analyses may thus be a suitable means of better understanding and controlling the epidemic course. An age, period, and cohort back-calculation method was used to reconstruct region-specific epidemics of HIV infection. The HIV infection incidence rates were estimated for individual Italian regions by using as denominator the specific risk category population (i.e. intravenous drug user population [IDU], homosexual/ bisexual population [MSWM], and Italian general population for heterosexual contacts [HST]). Incidence rates obtained in this way represent the risk of HIV infection conditional to belonging to the specific sub-group of the population. The HIV epidemic is heterogeneous in terms of gender, risk category and region. The highest risk of HIV infection has been estimated in the Lombardia region (North-West area) among men belonging to the IDU category in 1985. In recent years, a trend of decrease in HIV has been estimated, especially among IDU and MSWM. For the HST category, some regions have shown trends of great increase, particularly on the island of Sardegna and the regions of Puglia and Sicilia (Southern Italy). In 1987, most HIV infections were observed among IDU (39-90%), while in 1992 the MSWM and HST categories made the greatest contribution to the HIV epidemic. The results stress the idea of sub-epidemics rather than a single epidemic affecting the entire country. Some Southern regions emerge as areas in which the spread of HIV infections, although still at a rather low level, should cause considerable concern, particularly the trend of new infections by heterosexual transmission involving the general population. Detailed information on levels and trends of HIV infection epidemics at the local level are essential for surveillance purposes and for planning health care facilities, and can highlight areas in which preventive measures can be effective.