Tracing the evolutionary trajectory of Japanese encephalitis virus across hosts and countries.

Japanese encephalitis Virus (JEV), the leading cause of epidemic encephalitis worldwide, is widespread across Asia and Australia cycling between vertebrate reservoir hosts and culicine mosquitoes. Change in dominant genotype, epidemics in new regions and re-emergence of dormant genotypes pose major public health concerns. To investigate the prevalent genotypes and their host range, JEV isolates were compiled from NCBI GenBank over a period of eight decades and full-length envelope gene sequences were analyzed. TMRCA analysis confirmed that JEV originated in the Indonesia-Malaysia region and subsequently diversified into multiple genotypes. Intriguing trends in the genotype distribution and the spread of the virus across various hosts and regions were observed. A notable change from GIII to GI is observed in many countries and distinct emergence and dispersion patterns across different regions and time periods were documented. The re-emergence of GIV in Indonesia after 37 years, coupled with its emergence in Australia highlight the need for critical control measures. Similarly, GV's resurgence in China after 57 years and its circulation in Korea emphasize the necessity of continuous genomic surveillance. Whole genome analysis further reinforced these findings, revealing a broader host range and deeper evolutionary insights, underscoring the urgency of proactive public health interventions.