Viral hepatitis in Danish clinical chemical laboratories 1968--1978: incidence rates, aetiology and risk factors.

The occurrence of viral hepatitis in Danish clinical chemical laboratories during a 10-year period was studied by repeated questionnaires. The overall incidence rate was 180 per 100,000 per year, roughly 7 times the figures for the general population, the excess frequency being found for technicians, student technicians as well as in cleaning staff. 90% of the cases studied were HBsAg positive. Two clusters of cases were associated with a haemodiolysis and a cancer chemotherapy unit, respectively. Otherwise the hepatitis risk was 3 times greater in the metropolitan area than in provincial towns. Within the last 3 years the incidence rate decreased to one quarter of previous rates. This change might be attributable to increased general attention and safety precautions.