Abstract
The authors encountered an outbreak of acute hepatitis in "G" junior high school in Gifu prefecture between February and March, 1978. Hepatitis A virus particles were detected in faecal specimens collected from 5 pupils at the beginning of the outbreak.
In this paper, anti-HA was examined by radioimmunoassay in the sera of pupils, staff members, and family members of patients with hepatitis A. From the results of serological examination, number of patients with hepatitis A amounted to 109 persons including 6 persons of secondary infection (3 pupils, 2 adults and one child).
The discovery of patients in time by mass survey and personal prevention, such as handwashing, were significant to the prevention of secondary infection of hepatitis A.
