Japanese encephalitis (JE) is a mosquito-borne encephalitis caused by a group B arbovirus (Flavivirus) and transmitled by culicine mosquitoes. It is a zoonotic disease, i.e., infecting mainly animals and incidentally man. Twenty-five years ago, JE was known as an endemic disease in East Asia, especially in Japan, China and Korea. In recent years it has spread widely in SE Asia, and outbreaks of considerable magnitude have occurred in Thailand, Indonesia, Vietnam, India, Myanmar and Sri Lanka.
Animals and birds are the extra-human hosts. The basic cycles of transmission are:
The disease is transmitted to man by the bite of infected mosquitoes. Man is an incidental "dead-end" host. Man to man transmission has not so far been recorded.
Incubation Features : In man the incubation period varies from 5 – 15 days.
Stages of Disease in Man: three stages-
- Prodromal stage: acute onset associated with fever, headache and malaise. Lasts for 1-6 days.
- Acute encephalitic stage: high fever, focal CNS signs, convulsions, altered sensorium progressing to coma.
- Late stage and sequelae: starts at the end of active inflammation.
Control: Vector control and vaccination are the means of control