Japanese encephalitis also may occur with a lower frequency in Japan, Taiwan, Singapore, Hong Kong, and eastern Russia. In all areas, Japanese encephalitis is primarily a rural disease.
Transmission is usually seasonal, following the prevalence of mosquitoes.
In China, Korea and other temperate areas, the transmission season extends through the summer and fall. In other subtropical and tropical regions, risk is associated with the rainy season, which varies in each country. For instance, recent epidemics have occurred in northern India, Nepal, and Sri Lanka, from October to December. However, in tropical areas, sporadic cases may occur at any time of the year. The chance that a traveler to Asia will develop Japanese encephalitis is probably very small.