An outbreak of intrafamiliar hepatitis A associated with clam consumption: epidemic transmission to a school community.

An outbreak of hepatitis A is described involving thirteen cases in a town in central-northern Italy. The consumption of infected clams, caught in a polluted coastal area of the Adriatic Sea, caused hepatitis A in all five members of a family consisting of mother, father and children, two of whom attended primary school. The epidemic subsequently spread to the primary school with a secondary attack rate of 7.9%, 0 for female pupils and 18.9% for males. The epidemiological and environmental investigations showed that the critical exposure took place in the boys' toilet in the primary school (OR: 32.79, 95% CI: 6.83-157.45). To prevent the spreading of contagion, extra disinfection was carried out in the whole school and health education campaigns were mounted. The good basic hygienic conditions of the homes, together with the cooperation of school staff in surveillance and providing information, allowed the epidemic to be controlled.