AN OUTBREAK OF HEPATITIS-A AMONG HOMOSEXUAL MEN IN AMSTERDAM, 1991-1993

Background. When in August 1992 it became evident that an outbreak of hepatitis A virus infections (HAV) was taking place in the male homosexual community in Amsterdam a case-control study was conducted to validate the assumption that the outbreak was associated with sexual practices involving oro-anal and digital-anal contact and frequent visits to gay saunas and darkrooms. Methods. In all, 37 cases reported to the Amsterdam Municipal Health Service (AMHS) in the period December 1991 to March 1993 and 68 anti-HAV negative controls completed an anonymous questionnaire concerning the practice of different sexual techniques and the number of visits to gay saunas and darkrooms in the 2 months preceding the onset of illness or date of interview. Controls were recruited from healthy homosexual men participating in a prospective study on HIV/AIDS conducted by the AMHS. Results. In univariate analysis a statistically significant association was found between visits to gay saunas and darkrooms, the number of visits to these locations (OR = 8.2) and HAV infection. In the logistic regression analysis the association for visits to saunas and darkrooms remained significant (OR = 10) whereas high-risk sexual techniques could not be included in the model. Conclusions. These results indicate that to prevent future outbreaks of HAV in male homosexuals in Amsterdam there is a need to stress in the 'safe sex' campaigns, directed at the prevention of HIV infection or in additional campaigns, the prevention of other sexually transmitted disease including HAV infection with emphasis on routes associated with certain sexual techniques and on visits to gay saunas and darkrooms.