Hepatitis A outbreak reported among gay men in Norway

Following a similar report from London, the Norwegian Department of Infectious Disease Epidemiology has reported an outbreak of sexually transmitted hepatitis A among gay men. The report was published in the October 21^st edition of Eurosurveillance Weekly.

Up to 18^th October this year, 150 cases of hepatitis A were reported to the Norwegian Surveillance System for Communicable Diseases. This compares with 52 cases for the same period in 2003.

An analysis of the data found that 69 cases were probably or possibly due to sexual transmission between gay men. Fifty-one were from Oslo, four were from Bergen on the west coast while the others were scattered around the southern part of the country between the two cities. The mean age of the men was 43. No cases of spread to domestic partners via non-sexual routes were found.

The outbreak of the apparently related cases started in late May 2004, and peaked during July and early August, with six to ten cases a week over this period. They gradually tailed off during August and September, with the last confirmed case in the first week of October. Free hepatitis A vaccine was provided for gay men in Oslo and Bergen, which probably helped to contain the outbreak; normally patients have to pay for it. There has also been a campaign among Oslo gay venues warning of the increasing risk of hepatitis A and other sexually transmitted infections.

Norwegian regulations allow information on the route of transmission to be obtained in the case of hepatitis A but not the sexual orientation of subjects. Cases were regarded as ‘probably’ due to gay sex if they were a confirmed case of infection with genotype 1A, with sexual transmission as the cited route in a man aged between 17 and 69. Cases of hepatitis A in men between these ages but without other risk factors such as intravenous drug use or travel to countries with high hepatitis A prevalence were regarded as ‘possibly’ transmitted by gay sex.

Eighteen samples from the 69 apparently gay men were genotyped and found to be genotype 1A of the virus. This subtype of hepatitis A was found to be the cause of a similar outbreak reported from Copenhagen, Denmark and Malmö, Sweden earlier this year (Mølbak 2004).

Unlike the previous outbreak of sexually transmitted hepatitis A among gay men in Norway (Stene-Johansen 2002), no specific gay venue was found to be associated with this outbreak.

Outbreaks of sexually transmitted hepatitis A among gay men in Europe appear to be becoming more frequent, with outbreaks reported in London in 1997, Oslo and Rotterdam in 1998, Paris in 2000, Munich in 2003 and London, Oslo, Copenhagen / Malmö and the Netherlands in 2004.