Molecular epidemiology of hepatitis B virus infections in Denmark.
BACKGROUND
Denmark has a low incidence of acute hepatitis B (HBV) infections but the impact of an increasing number of immigrants with chronic HBV infection on HBV transmission is unknown.


OBJECTIVE
To characterise individuals with chronic and acute HBV infection in a defined region and to examine the importance of different risk groups for the current HBV transmission.


METHODS
During 2000-2001 all consecutive HBV infected individuals routinely diagnosed through the regional HBV serology laboratory in the County of Funen were classified according to ethnicity, presumed route of transmission and stage of infection based on clinical data mainly supplied by the requesting physician. HBV DNA was sequenced and subjected to phylogenetic analysis.


RESULTS
Of 309 identified cases, 91 (29%) were classified as acute infection. HBV DNA sequencing was possible in 54 (59%) of these cases. Phylogenetic analysis showed that HBV isolated from injecting drug users (IDUs) was identical or closely related. Among acute cases acquired in Denmark 89% (74/83) were seen in IDUs (65) or in individuals presumably exposed to IDUs (nine) and phylogenetic analysis corroborated the assumption of IDU related transmission in every case with available sequence data. Among 83 ethnic Danes who acquired their HBV infection in Denmark, no new cases of transmission from immigrants were detected.


CONCLUSIONS
Injecting drug use was the single most important factor for hepatitis B transmission in Denmark. The current Danish vaccination strategy is unable to protect IDUs from HBV infection and IDUs pose a greater risk of HBV transmission to the general population than immigrants.
Department of Clinical Immunology, Odense University Hospital, Sdr. Boulevard 29, DK-5000 C, Denmark. niels.fisker@dadlnet.dk
Niels
N
Fisker
Court
C
Pedersen
Marianne
M
Lange
Nga Thien Tich
NT
Nguyen
Kim Thien Tich
KT
Nguyen
Jørgen
J
Georgsen
Peer Brehm
PB
Christensen
D004279:DNA, Viral / Q000737:chemistry / Q000302:isolation & purification; D003718:Denmark / Q000453:epidemiology; D004641:Emigration and Immigration; D006509:Hepatitis B / Q000453:epidemiology* / Q000821:virology; D006515:Hepatitis B virus / Q000235:genetics* / Q000302:isolation & purification; D019694:Hepatitis B, Chronic / Q000821:virology; D006801:Humans; D017720:Molecular Epidemiology; D010802:Phylogeny; D012307:Risk Factors; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D015819:Substance Abuse, Intravenous / Q000150:complications / Q000821:virology
D004279:DNA, Viral