ABSTRACT
A sharp but short outbreak of hepatitis A occurred in a college during September and October 1992. The epidemic pattern suggested a common source. The attack rate of clinically recognizable hepatitis A was 8% all cases were HAV IgM positive. Among 31 students with minor symptoms but without jaundice 8 (26%) were also HAV IgM positive, as were 8 (10%) of 77 totally asymptomatic students tested. A case control study of eating and drinking habits of the students showed no other significant differences other than that 45 of 56 cases and 18 of 34 controls interviewed had filled their water glasses by dipping them in a overflow water reservoir. This gives an odds ratio of 3.8. The reservoir was heavily contaminated with coliform bacteria and the residual chlorine was at lower than standard concentration, whereas other water resources were clean. It is suggested that the reservoir had been contaminated with hepatitis A virus by somebody with fecally contaminated hands a couple of weeks prior to the beginning of the outbreak.