Clinically Apparent and Inapparent Infection with Japanese B Encephalitis Virus in Shanghai and Tientsin

SummaryComplement fixation tests on acute and convalescent sera established the virus of Japanese B encephalitis as the cause of acute encephalitis in a Chinese physician in Shanghai during July, 1946. Evidence of extensive, inapparent dissemination of this virus among the populations of Shanghai and Tientsin, where no epidemics of encephalitis have been observed, was obtained when neutralizing antibodies for the Japanese B encephalitis virus were found in 85% of 13 Chinese residents of Shanghai, aged 16 to 51, and in 89% of 19 life-long, Chinese residents of Tientsin, aged 17 to 57, all without history of encephalitis. Since the great majority of human beings escape with inapparent infection even in Japan, where severe epidemics have occurred, the question is raised whether the unknown factors, which predispose to clinically apparent infection, may be found less frequently among the Chinese than among the Japanese.