We evaluated the risk of hepatitis C virus transmission through household contact with chronic carriers using nucleotide sequence analysis. Chronic hepatitis C patients (76 patients) were divided into two groups: familial transmission of hepatitis C virus was studied in group A (53 patients); group B (23 patients) served as nonfamilial controls for group A. Of 88 family members of group A patients, 18 (20%) had elevated serum ALT levels, 20 (23%) had antibodies against hepatitis C virus and 16 (18%) had hepatitis C virus RNA in serum. Nucleotide sequences of the region of the hepatitis C virus genome spanning the core and envelope genes were compared among the three groups. In group B, the average nucleotide sequence homology was 91.0% 2 2.29% (a pairwise comparison was made for each of the patients; n = 253). Isolates from two family members were significantly more homologous to isolates from corresponding patients in group A than to isolates from group B patients. Of the two isolates from family members, one was from a child whose mother was a patient (97.7% homology) and one was from a spouse (98.1% homology). These results strongly suggest familial transmission of the same hepatitis C virus strain. Further studies are necessary to elucidate the route of intrafamilial transmission. (HEPATOLOGY 1993; 17:s 7 1-9 76.)
Transmission of hepatitis C virus (HCV) (1, 2) through parented exposureincluding blood transfusion, drug abuse and occupational injury by needles contaminated with bloodis well documented (3-5). However, at least 50% of HCV patients do not have histories of such parented exposure (3, 4, 6, 7).
Although familial clustering of HCV infection has been demonstrated in epidemiological studies using existing HCV antibody (anti-HCV) assays (8-161, trans-