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Japanese encephalitis virus
Last reviewed: 08.07.2025
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Japanese encephalitis is a natural focal infectious disease transmitted by mosquitoes of the genus Culex and other genera of the subfamily Culicinae. The virus was first isolated in 1933 by the Japanese scientist M. Hayashi; in Russia, it was first isolated in 1938 during a comprehensive expedition to Primorye by A.K. Shubladze (1940) and A.A. Smorodintsev and V.D. Neustroev (1941). Japanese encephalitis is common in the south of East Asia, especially in Japan, where the incidence often reaches 250 per 100,000 population. In Russia, Japanese encephalitis is recorded in the southern regions of Primorye. In nature, the virus persists not only in arthropods, but also in various species of birds and bats. Japanese encephalitis cases are detected exclusively in the summer-autumn period. This is one of the most severe diseases with the highest mortality rate, ranging from 20 to 70 and even 80%, more often in the elderly and women.
The basis of the pathogenetic mechanisms are lesions of the vascular system both in the central nervous system and in all organs and tissues, where the virus intensively multiplies and spreads hematogenously. The incubation period is from 4 to 14 days.
The disease begins very acutely: temperature of 39 °C and above, impaired consciousness, coma and mental disorders often occur.
Death may occur within the first few hours. In a more favorable course, convulsions, generalized muscle strain, and paralysis develop. The acute period, from the very beginning of which meningeal syndrome is noted, lasts no more than 8-9 days. In the terminal stage of the disease, damage to vital stem centers and bulbar disorders are characteristic.
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