News: A new study found waning immunity to Japanese encephalitis virus may predispose individuals to more severe dengue, highlighting timing of JE vaccine boosters.
About Japanese Encephalitis (JE)
- Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus and a major cause of viral encephalitis in Asia.
- It belongs to the same genus as dengue, Zika, yellow fever, and West Nile viruses.
- Most JEV infections are mild or asymptomatic, but about 1 in 250 becomes severe, and among this severe cases the fatality rate can be as high as 30%.
- The incubation period is 4–14 days.
- Symptom : Severe disease presents with high fever, headache, neck stiffness, disorientation, coma, seizures, and spastic paralysis.
- Transmission through:
- Bites of infected Culex mosquitoes, mainly Culex tritaeniorhynchus.
- An enzootic cycle between mosquitoes, pigs, and/or water birds.
- Humans, once infected, do not develop sufficient viraemia to infect feeding mosquitoes.
- Seasonality: It is a warm-season epidemics in temperate Asia; year-round transmission in tropics/subtropics, intensifying during rains and pre-harvest in rice regions.
- Treatment: There is no specific antiviral therapy for Japanese Encephalitis. Encephalitis is a medical emergency and requires urgent supportive care..
- Prevention
- Vaccination: Safe and effective vaccines exist (inactivated Vero cell-derived, live attenuated, live recombinant). one inactivated and both live vaccines are WHO-prequalified.
- Policy: WHO recommends JE immunization where it is a public health priority, with strong surveillance and a one-time catch-up at introduction.
- Key facts
- First documented JE case: 1871 in Japan.
- Risk areas: 24 countries in South-East Asia and Western Pacific Regions have JEV transmission risk, which includes more than 3 billion people.
- JE primarily affects children.
- Most adults in endemic countries have natural immunity after childhood infection, but individuals of any age may be affected.
