prevalence of hiv-1 infection in 18 year old men in tuscany. the toscana collaborative group. | the main route of transmission of the human immunodeficiency virus type 1 (hiv-1) is sexual contact. a high proportion of young adults is exposed to this mode of transmission. therefore it is important to assess the level of hiv-1 prevalence among 18 year olds in italy. | 1995 | 8557436 |