Japanese encephalitis is a viral disease caused by flavivirus that affects the membranes of the brain. It infect humans and animals. The transmission of Japanese encephalitis virus to humans occurs through the bite of an infected mosquito, primarily the Culex species. the virus cannot be transmitted via person- to-person contact.http://images.gizmag.com/gallery_lrg/culex.jpg
This virus circulates in ardeid birds (egrets and herons). Pigs are amplifying hosts, whereby the virus multiply in pigs and infects mosquitoes that bites the infected pigs, but does not cause disease. The virus tends to affect the human populations only when the infected mosquito populations becomes too large, leading to an increase in the human biting rate.
It is estimated that there is nearly 68 000 clinical cases of Japanese encephalitis being reported globally each year, with up to 20 400 cases resulting in deaths. Japanese encephalitis primarily affects children, who has yet to acquired partial immunity. Most adults in endemic countries have natural immunity after childhood infection. However, Japanese encephalitis can still infect individuals regardless of their age.Source: http://www.who.int/water_sanitation_health/diseases/encephalitis/en/ and http://www.who.int/mediacentre/factsheets/fs386/en/