Genotype V Japanese Encephalitis Virus Is Emerging

Abstract

Japanese encephalitis (JE) is a global public health issue that has spread widely to more than 20 countries in Asia and has extended its geographic range to the south Pacific region including Australia. JE has become the most important cause of viral encephalitis in the world. Japanese encephalitis viruses (JEV) are divided into five genotypes, based on the nucleotide sequence of the envelope (E) gene. The Muar strain, isolated from patient in Malaya in 1952, is the sole example of genotype V JEV. Here, the XZ0934 strain of JEV was isolated from Culex tritaeniorhynchus, collected in China. The complete nucleotide and amino acid sequence of XZ0934 strain have been determined. The nucleotide divergence ranged from 20.3% to 21.4% and amino acid divergence ranged from 8.4% to 10.0% when compared with the 62 known JEV isolates that belong to genotype I–IV. It reveals low similarity between XZ0934 and genotype I–IV JEVs. Phylogenetic analysis using both complete genome and structural gene nucleotide sequences demonstrates that XZ0934 belongs to genotype V. This, in turn, suggests that genotype V JEV is emerging in JEV endemic areas. Thus, increased surveillance and diagnosis of viral encephalitis caused by genotype V JEV is an issue of great concern to nations in which JEV is endemic. Japanese encephalitis virus (JEV) is a mosquito-borne virus that causes Japanese encephalitis (JE) with significant morbidity and mortality. Five genotypes (genotype I–V) have been identified based on the nucleotide sequence of viral envelope (E) gene of JEV. To date, the only known strain of genotype V is Muar strain, isolated from patient in Malaya in 1952. Since then, no genotype V JEV has been detected in the world. In this study, the JEV strain, XZ0934, was isolated from mosquito samples collected in China in 2009. The full-length genome sequences of the XZ0934 strain was determined and founded to be the second strain of genotype V JEV based on the phylogenetic analysis using the complete genome and structural gene sequences. This suggests that genotype V JEV is re-emerging after 57 years (1952–2009). Therefore, increased surveillance and more effective diagnosis for cases of JE caused by genotype V JEV are needed.