Background. Official reports on AIDS surveillance mainly consist of ab
solute numbers of AIDS cases or cumulative incidence rates. More detai
led analyses focusing on the clusters of subepidemics within Italy see
med necessary for a better understanding and more accurate description
of the epidemic. Methods. Age-specific AIDS incidence rates were calc
ulated with reference to resident population by sex, calendar time and
geographical area. Age-standardized incidence rates, with the Italian
resident population in 1990 as standard, were used to present time tr
ends and geographical distributions. All analyses were repeated for in
jecting drug users, homosexual/bisexual men, heterosexual contacts and
individuals with other or undetermined risk factors. Results. Annual
incidence rates for AIDS in Italy increased over the study period. The
highest rates were observed in the North and in Sardinia, while South
ern regions showed generally lower rates. This heterogeneity was more
evident when examining small geographical areas (i.e. provinces). Epid
emics in some of the smaller provinces, such as Imperia and Livomo (No
rthwestern port towns), were shown to be important in that they greatl
y affect AIDS incidence rates in the regions in which they are located
. Conclusions. According to our analysis, the crude presentation of da
ta from the Italian AIDS Registry is not adequate for understanding th
e national spread of the AIDS epidemic in terms of several local subep
idemics, which may differ by size, temporal trend, and risk group comp
osition. Classifying cases according to their place of residence, whic
h we considered as a good proxy of the place of life, was fundamental
for correctly locating these subepidemics. Furthermore, the use of age
-standardized rates allowed for unbiased comparisons between regions w
hose population may have a different age structure and dynamics.