[Hepatitis A outbreak in a kindergarten]

In November/December 1990 eight out of 38 children of a kindergarten in Basle were involved in an outbreak of hepatitis A, and further cases occurred among family members and friends of the children. A questionnaire survey and a serologic analysis including all families associated with the kindergarten was undertaken to investigate the source, extent and spread of the hepatitis A. Among 147 persons examined, 20 clinical cases of hepatitis A were diagnosed (9 adults, 11 children), 5 more children were unapparently infected. The hepatitis A virus was imported by an adult who contracted the disease during a journey to Mexico. The virus spread from person to person, the third case being the kindergarten child, who was responsible for the actual outbreak. In a first phase, 11 persons were affected, 6 of them children from the kindergarten. The second phase involved 5 adults and another child from the kindergarten. The hygienic measures undertaken in the kindergarten proved to be efficacious; only one further child was infected thereafter. Immunoglobulin was protective if administered in time. Only 2 out of 21 passively immunized persons who had had contact with hepatitis A patients contracted an unapparent infection, but without further transmission. Among 82 persons who were passively immunized too late or not at all, 20 fell clinically ill with hepatitis A and 3 were unapparently infected. Use of the newly available hepatitis A vaccine is discussed.