Japanese encephalitis is an infectious disease transmitted to humans through the bite of infected mosquitoes of the genus Culex . The responsible agent is a Flavivirus (to which also the viruses responsible for dengue and yellow fever belong).
Culex mosquitoes become infectious, having stung and fed on the blood of migratory birds (such as herons) and domestic animals (mainly pigs) that "host" the Japanese encephalitis virus and are the reservoir of the infection.
In humans, the incubation period can vary from 5 to 15 days. Infections can be asymptomatic or give rise to different manifestations (such as aseptic meningitis or undifferentiated febrile illness); actual encephalitis occurs from 1 to 20 cases per 1000 infections with headache, fever, neck stiffness, vomiting, convulsions, disorientation, altered state of consciousness, focal neurological deficits, motor disorders and coma. Sometimes, Japanese encephalitis can present itself as a parkinsonian syndrome or with a clinical picture similar to poliomyelitis.
Japanese encephalitis involves death in almost 20-30% of subjects. Coma, if not fatal, can be resolved in 1-2 weeks. Those who survive, however, can report permanent neurological disorders such as spastic tetraparesis, hemiplegia, difficulty swallowing and severe cognitive deficits.
There is no specific antiviral treatment for Japanese encephalitis, but the patient undergoes intense therapy to alleviate symptoms and careful monitoring until the infection is overcome.
