An outbreak of hepatitis A among young men associated with having sex in public venues.

An increase in hepatitis A virus (HAV) infection was noted among young men in the former Thames regions during 1997. A retrospective case-control study, using a standardised questionnaire at interview, was conducted in the area most affected (London and East Sussex) to investigate the hypothesis that this increase was mainly among homosexual men and to establish the risk factors associated with transmission. Forty-eight cases and 161 controls completed questionnaires. Forty-one cases (85%) described their sexuality as homosexual (p < 0.0001). Cases were more likely than controls to have eaten shellfish (Odds Ratio (OR) 2.4; 95% Confidence Interval (CI) 1.16, 5.04) during the two months before onset of illness. Cases had more sexual partners (p = 0.015), and more casual sexual partners (p = 0.007) than controls. Cases were more likely to have had sex in a gay sauna (OR 3.5; 95% CI 1.53, 8.30), or in a gay club, pub or disco (OR 2.9; 95 CI 1.29, 6.63) than controls. After adjusting for confounding factors, cases were more likely to have eaten shellfish (adjusted [adj] OR 3.0; 95% CI 1.33, 6.59) and to have had sex in a gay sauna (adj OR 3.9; 95% CI 1.42, 10.59). Public health messages need to inform homosexual men about recognised risk factors such as eating shellfish and travel abroad to endemic areas, as well as sexual risks. Homosexual men can benefit from hepatitis A vaccine. We would suggest that in an outbreak situation men who have multiple anonymous partners and have sex in public venues should be targeted as a priority for health education and immunisation.