Shift in Japanese encephalitis virus (JEV) genotype circulating in northern Vietnam: implications for frequent introductions of JEV from Southeast Asia to East Asia.
This study analyses the evolutionary relatedness of 16 Japanese encephalitis virus (JEV) isolates (nine from Vietnam and seven from Japan) to previously published JEV strains using E gene sequence data. Vietnamese and Japanese strains isolated between 1986 and 1990 were found to cluster in genotype 3. However, more recent Vietnamese and Japanese strains isolated between 1995 and 2002 grouped within genotype 1, now a dominant though previously unreported genotype in Vietnam. In addition, in this study, strains isolated between 1995 and 2002 were more closely related to those isolated in the 1990s than to the older genotype 1 strains. Recently, the introduction of JEV genotype 1 into Japan and Korea has also been reported. Hence this genotype shift phenomenon may be occurring throughout all East Asia. Further studies on JEV ecology are needed to clarify the mechanism of JEV genotype 1 spread to new territories.
Nga
Phan Thi
PT
Department of Virology, National Institute of Hygiene and Epidemiology, 1 Yersin Street, Hanoi, Vietnam.
Parquet
Maria Del Carmen
MDC
Department of Virology, Institute of Tropical Medicine, Nagasaki University, Sakamoto 1-12-4, Nagasaki City 852-8523, Japan.
Cuong
Vuong Duc
VD
Department of Virology, National Institute of Hygiene and Epidemiology, 1 Yersin Street, Hanoi, Vietnam.
Ma
Shao-Ping
SP
Division of Epidemiology, Department of Infectious Diseases, Oita Medical University, Hasama-machi, Oita, Japan.
Hasebe
Futoshi
F
Department of Virology, Institute of Tropical Medicine, Nagasaki University, Sakamoto 1-12-4, Nagasaki City 852-8523, Japan.
Inoue
Shingo
S
Department of Virology, Institute of Tropical Medicine, Nagasaki University, Sakamoto 1-12-4, Nagasaki City 852-8523, Japan.
Makino
Yoshihiro
Y
Division of Epidemiology, Department of Infectious Diseases, Oita Medical University, Hasama-machi, Oita, Japan.
Takagi
Masahiro
M
Department of Vector Ecology and Environment, Institute of Tropical Medicine, Nagasaki University, Sakamoto 1-12-4, Nagasaki, Japan.
Nam
Vu Sinh
VS
Department of Epidemiology, Entomology Laboratory, National Institute of Hygiene and Epidemiology, 1 Yersin Street, Hanoi, Vietnam.
Morita
Kouichi
K
CREST, Japan Science and Technology Corporation, Saitama 332-0012, Japan.|Department of Virology, Institute of Tropical Medicine, Nagasaki University, Sakamoto 1-12-4, Nagasaki City 852-8523, Japan.
D000818:Animals; D001210:Asia, Southeastern; D004664:Encephalitis Virus, Japanese / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D005202:Asia, Eastern; D005838:Genotype; D006801:Humans; D010802:Phylogeny; D014744:Vietnam