Molecular epidemiology of hepatitis A virus in metropolitan areas in Japan.
BACKGROUND
Transmission routes of hepatitis A virus (HAV) in Japan have changed. The present study investigated changes of transmission routes in relation to genetic drift.


METHODS
All 60 patients who were admitted between 1993 and 2003 with a diagnosis of hepatitis A were retrospectively analyzed. Nucleotide sequences of the VP1/2A region of the HAV recovered from their sera were determined.


RESULTS
The suspected transmission routes were household contact, 19 (31%); food or waterborne, 16 (27%); homosexual activity, 11 (18%); international travel, 4 (7%); and unknown 10. (17%). The 11 patients presumably infected through homosexual activity were found exclusively in 1998 and 1999. The proportion of patients exposed through homosexual behavior and household contact was higher in those 2 years than in other years. Nucleotide sequences could be determined for 58 patients. Fifty-seven of the 58 sequences belonged to genotype IA HAV, with less than 10% nucleotide diversity. Of the 27 sequences isolated during 1998 and 1999, 25 had an identical nucleotide sequence regardless of the suspected transmission route. In contrast, sequences obtained in the other years differed from one another. A phylogenetic tree constructed from sequences recovered from patients without a history of travel abroad showed several clusters.


CONCLUSIONS
Our results suggest that (1) HAV acquired through homosexual activity may be transmitted to nonhomosexual individuals; (2) hepatitis A in metropolitan areas in Japan is caused mainly by sporadic infection with genotype IA HAV; and (3) several subtypes of genotype IA HAV are endemic in Japan.
Takahashi
Hideaki
H
Department of Internal Medicine, Division of Gastroenterology and Hepatology, Institute of Medical Science, St Marianna University, Kawasaki, Japan.
Yotsuyanagi
Hiroshi
H
Yasuda
Kiyomi
K
Koibuchi
Tomohiko
T
Suzuki
Michihiro
M
Kato
Tomohiro
T
Nakamura
Tetsuya
T
Iwamoto
Aikichi
A
Nishioka
Kusuki
K
Iino
Shiro
S
Koike
Kazuhiko
K
Itoh
Fumio
F
D000328:Adult; D000914:Antibodies, Viral / Q000032:analysis*; D005260:Female; D006506:Hepatitis A / Q000453:epidemiology / Q000635:transmission / Q000821:virology; D030041:Hepatitis A virus / Q000235:genetics* / Q000276:immunology*; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D016133:Polymerase Chain Reaction; D012367:RNA, Viral / Q000032:analysis*; D012189:Retrospective Studies
D000914:Antibodies, Viral; D012367:RNA, Viral