Intrafamilial transmission of hepatitis delta virus: molecular evidence

BACKGROUND/AIMS: Epidemiologic studies have suggested that transmission of hepatitis delta virus (HDV) occurs by intrafamilial routes in some populations in southern Italy, where HDV infection is endemic. To further evaluate intrafamilial transmission of HDV, we obtained the partial sequence of the viral genome from HDV-RNA positive members of families in which two or more immediate family members were positive for HDV-RNA. METHODS: The region analyzed was the semi-conserved region from nucleotides 908 to 1265. Sequences obtained from family members were compared with those obtained from a control group of 20 unrelated patients. RESULTS: The mean genetic divergence among HDV isolates was 2.8 +/- 1.7% within the 9 families analyzed, and 7.6 +/- 2.2% among the control group of unrelated individuals (p < 0.0001). A Receiver Operating Characteristic curve and Youden Index were used to define a cut-off value of 3.5% to discriminate sequence variations calculated within families and in the control group. CONCLUSIONS: The data indicate that in most family units, HDV-infected members harbored nearly identical strains of HDV, and provide molecular support that HDV infection can be transmitted within the family. Such spreading among family members highlights the role of inapparent transmission through personal contacts.