Epidemiology of hepatitis A in Amsterdam, October 1978--December 1979.

The epidemiology of hepatitis A was studied in Amsterdam during a 15 month period from October 1978 through December 1979. 349 cases of viral hepatitis were reported of which 135 were serologically identified as hepatitis A. The diagnosis was established by testing a single acute-phase serum sample with ELISA for the detection of hepatitis A IgM antibodies. Most cases were sporadic; there were no outbreaks involving more than three cases. A seasonal variation was recognized with the highest incidence in later autumn and early winter. The peak attack rate was found in the age group of 5--9 and a smaller peak was noticed in the age group of 30--34. Recent exposure to a known case of hepatitis A or to a jaundiced person was the probable source of infection in 27% of the patients; 23% contracted hepatitis A within 7 weeks of visiting a tropical or subtropical country and in 50% no source was found. 50 patients provided stool specimens within 2 weeks of the onset of jaundice. Specimens were examined for the presence of hepatitis A virus antigen by ELISA and seven patients had positive stools, all within the first week of the onset of jaundice.