[An outbreak of hepatitis A among intravenous drug addicts in Oslo 1995-96].

Intravenous drug abuse is a well-known risk factor for acquiring hepatitis A infection. Among drug abusers most cases are sporadic, but epidemic outbreaks may occur occasionally. In this article we describe an epidemic outbreak including 144 serologically proved cases of hepatitis A among intravenous heroin and amphetamine abusers in Oslo. The outbreak lasted for 11 months. 59 (41%) of the patients were admitted to hospital. One of them died and seven developed severe but reversible acute hepatitis. We also registered 26 cases of hepatitis A among close contacts, 14 of whom were associated with a nosocomial outbreak that affected nurses, fellow patients and relatives. We do not know how the hepatitis A virus was introduced into the abuser population, but the further spread was probably dominated by a combination of faecal-oral transmission and parenteral transmission secondary to sharing needles. Although we were unable to detect hepatitis A virus in confiscated drug samples by means of polymerase chain reaction we cannot exclude that some abusers were infected by injection of contaminated amphetamine.