Intrafamilial transmission of hepatitis-C virus among the population of an endemic area of Japan.

OBJECTIVES: To assess the role of intrafamilial transmission of hepatitis C virus (HCV) among general populations.

DESIGN AND SETTING: Cross-sectional study in an HCV-endemic area of Japan.

PARTICIPANTS: A total of 1122 residents (mean age, 41.7 years; range, 0 to 80 years), including 359 mother-child pairs and 234 pairs of spouses.

MAIN OUTCOME MEASURES: Antibody to HCV (anti-HCV) was examined using second-generation anti-HCV testing by passive hemagglutination assay. Hepatitis C virus RNA was detected by polymerase chain reaction with primers deduced from the 5'-noncoding region and HCV genotypes by reaction with type-specific primers deduced from the HCV core gene.

RESULTS: Prevalence of anti-HCV was 14.1% (158/1122), and HCV RNA was detected in 82.9% of those who tested positive for anti-HCV. Prevalence of anti-HCV increased with advancing age, but no anti-HCV was found among 312 persons younger than 20 years. Of the 53 children with anti-HCV-positive mothers, three were positive for anti-HCV, all were older than 20 years, and all had a history of surgical treatment. Hepatitis C virus RNA was found in one mother-child pair but with different HCV genotypes. Both spouses were positive for anti-HCV in 17 of 234 pairs. Of the 11 pairs of spouses in whom the HCV genotypes of both were determined, five had different HCV genotypes.

CONCLUSIONS: While HCV is highly endemic in this area, neither vertical nor horizontal transmission between spouses seems to play an important role in its spread. The incidence of intrafamilial transmission of HCV seems to be low.