An outbreak of foodborne hepatitis A showing a relationship between dose and incubation period.

Seven of eleven persons who attended a picnic developed symptoms of hepatitis A, two and a half to five weeks later. The epidemiologically implicated source was tuna salad, served in sandwiches and prepared by the index case. The number of sandwiches consumed was inversely related to the incubation period. This phenonemon may explain some of the variability of incubation periods for hepatitis A.