Severe disease is characterized by rapid onset of high fever, headache, neck stiffness, disorientation, coma, seizures, spastic paralysis and ultimately death. In children, gastrointestinal pain and vomiting may be the dominant initial symptoms. The incubation period is between 4-14 days. Most JEV infections are mild (fever and headache) or without apparent symptoms, but approximately 1 in 250 infections results in severe clinical illness. Most adults in endemic countries have natural immunity after childhood infection, but individuals of any age may be affected. A literature review estimates nearly 68 000 clinical cases of JE globally each year, with approximately 13 600 to 20 400 deaths. The annual incidence of clinical disease varies both across and within endemic countries, ranging from 10 per 100 000 population or higher during outbreaks.
The first case of Japanese encephalitis viral disease (JE) was documented in 1871 in Japan. It is a mosquito-borne flavivirus, and belongs to the same genus as dengue, yellow fever and West Nile viruses. Japanese encephalitis virus JEV is the most important cause of viral encephalitis in Asia. WHO recommends that JE vaccination be integrated into national immunization schedules in all areas where JE disease is recognized as a public health issue. Safe and effective vaccines are available to prevent JE.Treatment is focused on relieving severe clinical signs and supporting the patient to overcome the infection. 24 countries in the WHO South-East Asia and Western Pacific regions have endemic JEV transmission, exposing more than 3 billion people to risks of infection.Permanent neurologic or psychiatric sequelae can occur in 30%–50% of those with encephalitis. Although symptomatic Japanese encephalitis (JE) is rare, the case-fatality rate among those with encephalitis can be as high as 30%.JEV is the main cause of viral encephalitis in many countries of Asia with an estimated 68 000 clinical cases every year.Japanese encephalitis virus (JEV) is a flavivirus related to dengue, yellow fever and West Nile viruses, and is spread by mosquitoes.