Outbreak of Hepatitis B among injecting drug users in Denmark

Background: The incidence of hepatitis B is low in Denmark, but injecting d rug users (IDUs) remains a high-risk group for this infection. Objectives: The aim of the study was to describe a hepatitis B outbreak among IDUs by c omparing existing registers. Additionally, we wanted to analyze the genetic variation of the hepatitis B virus involved in the outbreak. Study, design : In the County of Funen, registers of laboratory diagnosis, hospital recor ds and reports from clinicians to the Medical Officer of Health (MOH) were compared between 1992 and 1998. HBsAg positive sera recovered from the epid emic were sequenced and compared to known HBV strains. Results: We identifi ed 648 cases of hepatitis B of which 51% (332) were acute infections. The l aboratory database identified 96% (319/332) of these, 45% (150/332) were ad mitted to hospital and 38% (127/332) were reported to public health. By cap ture-recapture analysis based on MOI-I reports and hospital records the est imated total number of acute cases were 334 (95% C.I, 283-385). We sequence d 75 HBsAg positive samples and identified two very similar strains of geno type D (serotype ayw3) among IDUs involved in the outbreak. Conclusions: Th e current surveillance system did not detect the majority of acute hepatiti s B cases in County of Funen. We suggest laboratory-based surveillance of h epatitis B to be implemented at a national level as this may identify new o utbreaks faster and more complete than the current surveillance system. (C) 2001 Elsevier Science B.V. All rights reserved.