Intrafamilial clustering of genotypes of hepatitis C virus RNA.

Hepatitis C virus (HCV)-RNA in the blood was measured by polymerase chain reaction (PCR) in 37 subjects from eight families in which 2 or more persons tested seropositive for antibodies against C100-3 or CP9. HCV-RNA was positive in 17 of 37 subjects. Two or more HCV-RNA-positive subjects were observed in six of the families. Intrafamilial HCV infection was studied by determining the HCV-RNA type (I, II, III or IV) by PCR using type-specific primers. In two families, all of the subjects showed type III infection, and in three other families, all of the subjects showed type II infection, with different types of HCV infections being observed in only one family. The HCV type was uniform in all but one. These findings suggest a possibility of intrafamilial infection between husbands and wives and between members of the same household.