When Japanese Encephalitis Virus Invaded Eastern Hemisphere – The History of the Spread of Virus Genotypes

When Japanese Encephalitis Virus Invaded Eastern Hemisphere -The History of the Spread of Virus Genotypes 407 JEV is supposed to have evolved in other genotypes from the most divergent and probably oldest genotypes (GIV and GV), that have only be found in Indonesia-Malaysia region, and that JEV has spread from this region across Asia.Although it was classically accepted that genotypes I and III occurred mostly in epidemic regions (temperate region of Asia), while GII and GIV were associated with endemic disease (tropical region), and ultimately postulated that differences in strain virulence could explain the clinical epidemiology (Chen et al., 1990; Chen et al., 1992;Williams et al., 2000), limited experimental assay on mice were not conclusive (Solomon et al., 2003).Moreover, several more recent observations tend to discard this hypothesis and suggest that genotypes could be found indifferently within former epidemic or endemic area.Thus, two JEV strains belonging to GI were isolated in the Australasian region (Pyke et al., 2001) and strains of the genotype II have been shown to use to circulate in Korea before 1970's (Schuh et al., 2010, 2011). Japanese Encephalitis vaccineCurrently, three JEV vaccines are in use (Guirakhoo et al., 1999 ;Chang et al., 2000): (i) a formalin-inactivated, mouse brain-derived vaccine, based on the wild-type Nakayama or Beijing-1 strains, has been used internationally since the 1960s; (ii) a cell culture-derived inactivated vaccine; (iii) a cell culture-derived live attenuated vaccine, in China only.All vaccine types were developed from GIII JEV strains.Vaccine campaigns dramatically reduced the burden of the disease particularly in Japan, Korea, Taiwan, Sri Lanka, Thailand and Vietnam. Materials and methods Data collectionAmong 563 wild strains investigated, 512 Japanese encephalitis virus strains could be fully characteristics from the available literature, GenBank Nucleotide database (www.ncbi.nlm.nih.