Japanese Encephalitis


Adult Culex tritaenorhynchus
This section provides information on one of the nine zoonotic diseases which have been identified by a experts in a national consultation organised by RCZI in June, 2008  as focus or priority diseases for the next five years.

Japanese encephalitis is a mosquito-borne viral infection of birds, horses, pigs and humans. This virus can also infect other domesticated animals including cattle, sheep, goats, dogs and cats, as well as wild mammals, reptiles, amphibians and birds; these infections are typically asymptomatic. In countries where it is endemic, this virus causes reproductive losses in swine and encephalitis in horses. Birds serve as important reservoir hosts.

In humans, Japanese encephalitis can be a very serious disease: although most infections are asymptomatic, clinical cases tend to manifest as severe, often fatal encephalitis. Epidemics, which occur periodically in endemic regions, can cause significant morbidity and mortality in unvaccinated humans (case fatality rate of nearly 30%) and animals. Sporadic cases also occur in susceptible humans and animals throughout the mosquito season.


In1998-2004, JE was reported from 15 states
and Union Territories in India
Japanese encephalitis virus is usually transmitted by mosquitoes in the genus Culex. The specific mosquito vectors vary with the region; however, Culex tritaeniorhynchus is important in spreading this virus to humans and domesticated animals across a wide geographic range. C. tritaeniorhynchus breeds in rice paddies and connecting canals, and is active at twilight.

JE was first recorded in Vellore and Pondicherry in the mid 1950’s and the first major outbreak occurred in 1973 in Bankura and Burdwan districts of West Bengal before spreading to other states. The Directorate of National Vector Borne Disease Control Programme (NVBDCP) is the nodal agency responsible for controlling and preventing JE in the country. From 2568 cases reported and 707 deaths reported in 2003, the numbers have gone up to 3473 cases and 511 deaths in 2009. For more details on the disease and our work on Japanese Encephalitis, check our microsite.

Confirmed and Suspected Outbreaks of Japanese Encephalitis