AN OUTBREAK OF HEPATITIS-A AMONG IRISH HEMOPHILIACS

Background. An outbreak of hepatitis A (HAV) occurred in 1992 in Irish haemophilia A patients treated with high purity solvent-detergent (SD ) treated factor VIII. Similar outbreaks were reported in Italy, Germa ny and Belgium. The aim of this study was to investigate the outbreak, and to test the hypothesis that it was caused by exposure to SD-treat ed factor VIII. Methods. A case-control study was started in early 199 3. Haemophilia A cases with acute HAV (n = 29) were compared with haem ophilia A controls for exposure to SD-treated factor VIII and other en vironmental factors. Details of factor VIII usage were obtained from t he National Haemophilia Register and environmental data were obtained by a telephone-administered questionnaire. The response rate was appro ximately 90%. Results. The incidence of acute HAV infection among haem ophilia A patients exceeded the notified national incidence of HAV by a factor of approximately 300. The incidence was higher in younger pat ients and those with more severe bleeding disorders, Contact with hepa titis, with children, and exposure to factor VIII were associated with increased risk. The association with factor VIII was the strongest ri sk factor after controlling for other factors (odds ratio = 27.6, 95% confidence interval [CI] 6.5-117.3). A dose-response effect was demons trated. Conclusions. Although person-to-person transmission is likely to have caused a few of the cases, the results of our investigation su ggest that the major contributing factor was exposure to certain batch es of SD-treated factor VIII.