[Incidence of hepatitis virus infections and diseases in travelers returning from the tropics].

Travellers' hepatitis has been investigated by comparing clinical and serological data. The histories of 876 persons examined after their return from tropical countries were analysed for type, location, and length of stay abroad, prophylactic administration of gamma-globulin and past hepatitis. In addition to clinical investigations, 528 of the patients underwent radioimmunoassays for hepatitis markers. HBs antigen was detected in 1.1%, anti-HBs antibodies in 14.2%, and anti-HA antibodies in 37.3% of the patients. The prevalence of anti-HA antibodies increased with age, but the mean value for those over 20 years was only 8% above the mean for the corresponding age groups of Swiss residents. Significant differences in prevalence of anti-HA antibodies were only observed in persons who had stayed in the tropics for more than 5 years. The prevalence of hepatitis B markers was 2-3 times higher in persons returning from the tropics than in volunteer Swiss blood donors. Contrary to hepatitis A, the hepatitis B markers were related neither to age nor to the length of stay abroad. Patient's histories and serological tests revealed a high frequency of unapparent infections, i.e. 74% of hepatitis A and 88% of hepatitis B infections. Acute viral hepatitis was newly diagnosed in 17 out of the 2032 tropical patients who consulted us during 1979. The yearly incidence of hepatitis in this population was thus 8.5%, which is about 10 times higher than that estimated for the Swiss population as a whole. Only 5 of the 17 cases showed hepatitis of type A. One third of the cases were anicteric. The study clearly shows the importance of non-A hepatitis among travellers. In consequence, questions arise as to the prophylactic use of gamma-globulin and the epidemiology of traveller's hepatitis.