[Flavivirus Infection (Japanese Encephalitis)]

Japanese encephalitis remains a clinically relevant neuroinfectious disease in Japan. Adults in middle- to older- age groups are at higher risk due to the low prevalence of neutralizing antibodies. Clinicians should consider this disease when encountering acute encephalitis during the summer-to-autumn season. High fever, impaired consciousness, and extrapyramidal signs are characteristic clinical features and correspond to frequent involvement of the thalamus and substantia nigra. A definitive diagnosis is achieved through appropriate sampling of acute- and convalescent-phase specimens together with specific serologic testing. This article summarizes key clinical points of Japanese encephalitis that also inform the diagnostic approach to other flavivirus encephalitides.