Japanese encephalitis (JE) is a viral infection caused by the flavivirus related to Dengue , yellow fever and West Nile viruses, and is spread by mosquito bites of the Culex species. Symptoms take 5-15 days to appear after mosquito bites. Common symptom includes fever and headache. In serious cases, infection reaches the brain of patient leading to encephalitis or brain fever which go as high as 105 degree C . Other serious symptoms include neck stiffness, disorientation, coma, seizures and paralysis leading to death. Survivors suffer permanent intellectual, behavioral or neurological problems such as paralysis.
JEV is the main type of viral encephalitis in many countries of Asia. Around 7 lakh cases occur in Asia every year. It mainly affect children and young adults. Death occurs in 15 % of the cases. The deadly virus transmits from mosquitoes to pigs and water birds and make them their reservoir for further infection (zoonotic cycle). Disease is mainly found in rural and suburbs where locals live closely with these animals.
Transmission of disease can occur year-round but often create a havoc during the rainy season and pre-harvest period in rice cultivating regions. Mosquito breeding grounds are mainly paddy fields. In India, the endemic states are Tamil Nadu, Karnataka, Assam and Uttar Pradesh (Gorakhpur). Karnataka experiences two epidemics each year, with a severe form from April to July and a milder one from September to December along with the rest of India. Assam start having cases of JE from February onward attaining a peak in July. Other states report cases from July onward attaining a peak in September.
No effective antivirals but treatment based on support and care to relieve and stabilize the patient. Vaccination and preventing mosquito bites are preventive measures. Vaccination drives are done mainly before the onset of rainy season.