Japanese encephalitis virus (JEV) is a mosquito-borne RNA virus belonging to the genus Flavivirus, family Flaviviridae. It is the leading cause of viral encephalitis in Asia, including South and Southeast Asia. Humans are dead-end hosts, while pigs and wading birds act as amplifying reservoirs. Transmission occurs mainly through Culex mosquitoes (especially Culex tritaeniorhynchus).
Virus enters via mosquito bite → local replication → viremia
Crosses the blood–brain barrier → infects neurons
Causes inflammation, neuronal degeneration, and necrosis.
Results in acute encephalitis with high morbidity and mortality
Severe disease is common in children and non-immune adults
Fever, headache, vomiting
Altered sensorium, seizures
Parkinsonian signs, coma
High rate of neurological sequelae in survivors
Specimens
Cerebrospinal fluid (CSF)
Serum (acute and convalescent)
Diagnostic methods
IgM antibody detection by ELISA (CSF/serum) – gold standard
RT-PCR for JEV RNA (early phase)
Virus isolation in cell culture or mice (reference labs)
CSF findings: lymphocytic pleocytosis, mildly raised protein
No specific antiviral therapy is available.
Supportive management only:
Control seizures
Maintain airway and ventilation
Manage raised intracranial pressure
Fluid and electrolyte balance
Intensive care in severe cases
Vaccination (most effective)
Inactivated Vero cell vaccine
Live attenuated vaccine (SA 14-14-2)
Recommended for children in endemic areas and travelers
Vector control
Mosquito control measures
Elimination of breeding sites
Insecticide spraying
Personal protection
Mosquito nets, repellents
Protective clothing
Avoid outdoor exposure at dusk/night
Enveloped, positive-sense ssRNA virus
Transmitted by Culex mosquitoes
Humans = dead-end host
Pigs = amplifying host
Causes acute viral encephalitis
IgM ELISA in CSF = diagnostic test of choice
Prevention by vaccination is crucial.
