Changes in incidence of hepatitis B in Ireland from 1970–1987

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Abstract
This paper analyses data on 2,226 cases of Hepatitis B virus (HBV) infection detected during the years 1970 to 1987. Of those where information on risk-group was available (1,301), infection among intravenous drug-abusers accounted for the largest proportion (49%). Most became infected during and since an outbreak of hepatitis B and Delta hepatitis which originated in this group in 1980. A comparison of the data before and after the start of the outbreak among drug-abusers shows a marked increase in the number of HBV infections in nondrug users, including haemophiliacs, homosexuals and health-care staff, and a dramatic decrease in hepatitis B following blood transfusion. A larger group (165 cases), many of whom are long-term healthy hepatitis B surface antigen carriers, were patients in institutions for the mentally handicapped (IMH). Most were detected recently during pre-vaccination sampling programmes. Others affected included visitors to and from high-incidence areas, tattooed persons, dialysis patients, persons born to infected mothers, and members of the security forces dealing with drug-abusers. In all, 8.4% of the hepatitis B cases detected were found to be carriers and 67% of these remained carriers in 1987. The mean duration of carriage was 3.25 years. Intravenous drug-abusers and IMH patients constituted the two largest groups of carriers. The running-three-yearly mean incidence of new cases of hepatitis B has levelled off below the peak of 1981. Although the number of cases among drug-abusers has apparently decreased, the number of cases among non drugabusing groups has increased by 50%. The use of recently introduced vaccines in some risk groups should help to reverse this upward trend.