Transmission of Japanese Encephalitis Virus
Japanese encephalitis (JE) virus, a flavivirus, is closely related to West Nile and St. Louis encephalitis viruses. JE virus is transmitted to humans through the bite of infected Culex species mosquitoes, particularly Culex tritaeniorhynchus.
The virus is maintained in a cycle between mosquitoes and vertebrate hosts, primarily pigs and wading birds. Humans are incidental or dead-end hosts, because they usually do not develop high enough concentrations of JE virus in their bloodstreams to infect feeding mosquitoes.
JE virus transmission occurs primarily in rural agricultural areas, often associated with rice production and flooding irrigation. In some areas of Asia, these conditions can occur near urban centers.
In temperate areas of Asia, JE virus transmission is seasonal. Human disease usually peaks in the summer and fall. In the subtropics and tropics, transmission can occur year-round, often with a peak during the rainy season.