Japanese Encephalitis - A Plague of the Orient

Japanese encephalitis has attracted attention recently in the United States, Europe, and Australia because of a small number of cases among travelers, but the epidemic proportions of the disease in Asia have compelled immunization of entire regional or national populations. Japanese encephalitis, which is caused by a flavivirus transmitted by mosquitoes, often strikes in unpredictable form. It affects principally school-age children and is greatly feared because of its high lethality and frequency of permanent neurologic sequelae. The clinical disease was described as early as 1871 in Japan, but the causative agent was not isolated until 1934. A major summertime epidemic problem in Japan until the late 1960s, Japanese encephalitis has subsequently caused fewer than 100 cases annually.