Japanese Encephalitis

General Information

Japanese encephalitis is the disease that results from being infected by the mosquito-borne Japanese encephalitis virus. The disease is most prevalent in Southeast and Far Easy Asia and is the leading cause of viral encephalitis in Asia.

Domestic pigs and wild birds can often become reservoirs for the disease as they are often asymptomatic, allowing mosquitoes to pick up the disease from them and carry it to humans. Although there are 30,000-50,000 cases of Japanese encephalitis reported annually, it usually does not occur in urban areas.


Japanese encephalitis has an incubation period of 5 to 15 days, although most cases are asymptomatic with only 1 in 250 infections developing into full blown encephalitis. Non-specific symptoms include fever, headache and malaise lasting for a period of between 1 and 6 days. Symptoms that develop during the acute encephalitic phase include neck rigidity, cachexia (loss of weight, muscle atrophy, weakness, fatigue and severe loss of apetite), convulsions, hemiparesis (weakness on one side of the body) and a raised body temperature between 38 and 41 degrees Celcius.

There may be some occurrences of life-long neurological defects such as deafness, emotional lability (uncontrollable, excessive or inappropriate emotional responses such as laughter and crying) and hemiparesis in those who have had central nervous system involvement. Out of the known cases of Japanese encephalitis, some effects victims suffer also include, nausea, headache, fever, vomiting and sometimes swelling of the testicles.


There is currently no direct treatment for Japanese encephalitis, so treatment that is administered is supportive and aimed at the displayed symptoms. Recent research suggests that minocycline, currently in clinical trials for both Parkinson's disease and Huntington's disease, may be an effective treatment for the disease.


Japanese encephalitis can be prevented by receiving a vaccine. There are a number of vaccines currently available. Neutralizing antibodies spawned by the vaccine persist in the blood for at least two to three years after vaccination, maybe even longer. Because not enough is known about the total duration of protection, but due to the fact there is no firm evidence of protection after three years, those who remain at serious risk are advised to receive booster shots every two years.

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