“…Others, as the study by Hoxie et al (1990) carried out between 1986 and 1988, but published in 1990, concentrated its target much more on the relationship between ingress inmates and intravenous drug users (IVDUs). Almost at the same time, Vlahov et al (1991) carried out one of the most complete studies among 10,994 ingress inmates in ten different penitentiaries in USA, but the focus was the IVDUs before confinement and consequently cannot be compared with our data with regard to almost 700 inmates, from two different types of prison systems, and whose period of study was not longer than seven months.…”