Simultaneous infection with type A and B hepatitis viruses.

The occurrence of a common source hepatitis A epidemic among the residents of a New England state mental institution where hepatitis B is hyperendemic provided an opportunity to observe concurrent infections with both agents. Nine HBsAg-positive individuals developed hepatitis A infections documented by hepatitis A antibody seroconversion in eight. The incidence of hepatitis A infections in susceptible HBsAg-positive persons (67%) did not differ from that in HBsAg-negative individuals (63%). The icteric to anicteric infection ratio in the HBsAG-positives (1:1.7) was similar to that in the negatives (1:2.1), and the clinical course in the antigen positives did not differ significantly from that of the antigen negatives. In addition to confirming previous reports that the viruses of hepatitis A and B are immunologically distinct, these results document that infection with either is independent of the other, and that the morbidity from simultaneous infection is no greater than that caused by either alone.