Molecular epidemiology of hepatitis C virus infection among inravenous drug users

BACKGROUND/AIMS: The clinico-pathological features of hepatitis C virus infection in intravenous drug users are different from those found in other hepatitis C virus-infected patiens. Our aim was to test whether specific viral variants circulate within this particular patient population. METHODS: We studied the distribution of hepatitis C virus genotypes in 90 drug addicts and 484 controls, according to the method described by Okamoto. RESULTS: Hepatitis C virus type 1a and 3a infections were more frequent among intravenous drug users than in 125 age-matched controls (48.8% and 21.1% vs 17.6% and 11.2%), Accounting for the majority of infections in intravenous drug users. Analysis of hepatitis C virus genotype according to age showed that, in the general population, hepatitis C virus types 1a and 3a were more prevalent among patients younger than 40 years of age than in older individuals (17.6% and 11.2% vs 1.4% and 0.6%). CONCLUSIONS: These findings suggest that hepatitis C virus types 1a dn 3a were recently introduced in Italy, presumably via needle-sharing among intravenous drug users, and from this reservoire they are extending to the general population, particularly among younger subjects.