Tatsunori Nakano1, Kazuaki Takahashi2, Masaharu Takahashi3, Yoichi Nishigaki4, Naoki Watanabe4, Satoshi Ishida5, Shino Fujimoto5, Hideaki Kato6, Hiroshi Okano7, Yoshiyuki Takei8, Minoru Ayada9, Eiichi Tomita4, Masahiro Arai2, Hiroaki Okamoto3, Shunji Mishiro2. 1. Department of Internal Medicine, Fujita Health University Nanakuri Sanatorium, Mie, Japan. 2. Department of Medical Sciences, Toshiba General Hospital, Tokyo, Japan. 3. Division of Virology, Department of Infection and Immunity, Jichi Medical University School of Medicine, Tochigi, Japan. 4. Department of Gastroenterology and Hepatology, Gifu Municipal Hospital, Gifu, Japan. 5. Department of Internal Medicine, Kuwana West Medical Center, Kuwana, Japan. 6. Department of Forensic Medicine, Nagoya City University Graduate School of Medical Sciences, Aichi, Japan. 7. Department of Gastroenterology, Suzuka General Hospital, Mie, Japan. 8. Department of Gastroenterology and Hepatology, Division of Clinical Medicine and Biomedical Science, Institute of Medical Sciences, Mie University Graduate School of Medicine, Mie, Japan. 9. Department of Gastroenterology, Chutoen General Medical Center, Shizuoka, Japan.
Abstract
BACKGROUND & AIMS: Hepatitis E virus (HEV) genotype 4 has mainly been isolated from sporadic hepatitis cases and swine in Asian countries. We analysed the origin and global dispersal history of genotype 4 using a Bayesian phylogeographical approach. METHODS: The 412-nucleotide sequences of open reading frame 2 of genotype 4 (47 Japanese, 40 Chinese, 1 Indian, 8 Indonesian, 1 Korean, 1 Taiwanese, 2 Danish and 2 Italian), of which sampling date and location were known, were collected. Evolutionary rate, divergence time, demographic growth and phylogeography were co-estimated in the Bayesian statistical inference framework implemented in the BEAST package to model spatial dispersal on a time-scaled genealogy. RESULTS: The most probable origin of genotype 4 was Japan and the time of origin was 1909 (95% highest posterior density, 1871-1940). Seven lineages of genotype 4 migrated from Japan to China. The analysis also showed the migration of genotype 4 from Japan or China to India and Indonesia and from China to Indonesia, Taiwan, Korea and a few European countries. CONCLUSIONS: Swine trade between countries coincided with the migration time and direction of genotype 4 in some cases and was considered the primary cause of dispersal. However, there was no clear cause of dispersal for some cases, for which no records of pig trade were found. Future research should analyse additional nucleotide sequences paired with epidemiological data from various countries to improve our understanding of HEV dispersal.
BACKGROUND & AIMS:Hepatitis E virus (HEV) genotype 4 has mainly been isolated from sporadic hepatitis cases and swine in Asian countries. We analysed the origin and global dispersal history of genotype 4 using a Bayesian phylogeographical approach. METHODS: The 412-nucleotide sequences of open reading frame 2 of genotype 4 (47 Japanese, 40 Chinese, 1 Indian, 8 Indonesian, 1 Korean, 1 Taiwanese, 2 Danish and 2 Italian), of which sampling date and location were known, were collected. Evolutionary rate, divergence time, demographic growth and phylogeography were co-estimated in the Bayesian statistical inference framework implemented in the BEAST package to model spatial dispersal on a time-scaled genealogy. RESULTS: The most probable origin of genotype 4 was Japan and the time of origin was 1909 (95% highest posterior density, 1871-1940). Seven lineages of genotype 4 migrated from Japan to China. The analysis also showed the migration of genotype 4 from Japan or China to India and Indonesia and from China to Indonesia, Taiwan, Korea and a few European countries. CONCLUSIONS:Swine trade between countries coincided with the migration time and direction of genotype 4 in some cases and was considered the primary cause of dispersal. However, there was no clear cause of dispersal for some cases, for which no records of pig trade were found. Future research should analyse additional nucleotide sequences paired with epidemiological data from various countries to improve our understanding of HEV dispersal.