Hepatitis C virus infection in infants whose mothers took street drugs intravenously.

To assess the risk of transmission of hepatitis C virus from mother to infant during pregnancy or at delivery, we measured the antibody to hepatitis C virus (anti-HCV) by an enzyme-linked immunosorbent assay (ELISA) and a recombinant immunoblot assay (RIBA) in serum from 43 infants whose mothers took illicit drugs intravenously. Passively transmitted maternal anti-HCV was detected in 17 (40%) of the 43 infants tested with the ELISA during the first 4 postnatal months. Ten of these initially seropositive infants were followed to 15 months of age or beyond; anti-HCV cleared from nine infants and persisted in one. Among 24 initially seronegative infants, three (12.5%) showed persistent anti-HCV at 6, 11, and 18 months of age, respectively. The remaining two infants were initially tested with ELISA at 6 and 15 months of age; both were transiently seropositive, but anti-HCV disappeared by 12 and 24 months of age, respectively. Among the 17 infants with maternal antibody, nine with ELISA reactions greater than 2.5 optical density units were reactive by RIBA: the eight with weaker reactivity by ELISA were nonreactive by RIBA. When serum samples from the four infants who showed persistent reactivity by ELISA were tested with RIBA, one reacted to both antigens displayed by RIBA (C-100 and 5-1-1), one reacted to the 5-1-1 antigen only, and two were nonreactive. Serum transaminase values were elevated in three of these four infants; all four were also infected with human immunodeficiency virus. The results indicate that vertically transmitted hepatitis C virus may be a cause of hepatitis in infants, especially those coinfected with human immunodeficiency virus. Neonates at risk of hepatitis C virus infection should be monitored beyond 12 months of age. The interpretation of tests for anti-HCV antibody during infancy requires further investigation.