A large outbreak of hepatitis A in a day-care center: association with non-toilet-trained children and persistence of IgM antibody to hepatitis A virus.

In early summer, 1979, a large outbreak of hepatitis A occurred in an Oklahoma day-care center. A total of 41 cases were confirmed, all in adults. Of the 115 non-employee households represented by children in the center, 19 households (16.5%) had one or more cases of hepatitis. Hepatitis occurred in 29% of the households with at least one non-toilet-trained child, compared to 2% of the households without such a child (p = 0.00004). At least four (15%) of 27 center employees had hepatitis. Of 26 cases tested serologically, all were positive for hepatitis A antibody (anti-HAV), and 24 of these 26 were also positive for anti-HAV of immunoglobulin class M (anti-HAV IgM), at an average time after onset of illness of 80 days (range, 38-142 days). Three of ten persons remained anti-HAV IgM-positive 164 days after onset.