Japanese Encephalitis is primarily a rural disease. The mosquito transmits the virus via a vertebrate host, usually pigs or wild birds. The species is found in agricultural areas where the larvae develop in ground water, especially flooded rice fields. The mosquitoes bite in the late afternoon and early evening. Transmission Transmission is usually seasonal, following the prevalence of mosquitoes.
Epidemics usually occur towards the end of the wet season.
In north India and Nepal transmission occurs from June to November, and in south India and Sri Lanka epidemics are found from September to January. The total number of cases is estimated at more than 50,000 annually. The majority of infected persons develop mild symptoms or no symptoms at all. Symptoms and disease course Japanese Encephalitis has an incubation period of from four to 14 days, and is followed by a flu-like illness with headache, fever, muscle pains, and often gastrointestinal symptoms including vomiting. The illness often resolves without further complications.