Japanese encephalitis is a form of viral encephalitis caused by a particular strain of virus which is transmitted from host to host by mosquito bites. It is one of four similar viruses that are known to infect humans, one of the others being West Nile virus. In addition to infecting humans, it is also found in pigs and wild birds, which can serve as a reservoir for the virus. Despite it's name, it is endemic throughout south-east Asia and about 70,000 cases appear annually.
Symptoms can appear anywhere from 2-15 days after infection. In the vast majority of cases, patients are asymptomatic or have only mild symptoms. It only develops into encephalitis in about one out of every 250 infected people.
Initial symptoms are prosaic and non-specific, such as fever, headache and malaise. However, if the disease progresses to neck rigidity, severe weight loss, paralysis on one side of the body, convulsions and high body temperature.
The disease can be prevented by vaccination, and this is recommended for anyone travelling to endemic areas. However, once a case develops, treatment is supportive, including breathing support if necessary. The disease is not contagious.