An Epidemiological Study on the Susceptibility of Japanese People to Japanese Encephalitis Virus Infection by Season of Birth

Abstract

By means of comparing seasonal distribution of births between the Japanese encephalitis (JE) patients in the JE epidemics during 1948-64 and the general population in Tokyo, the susceptibility difference to an apparent infection of JE virus by their season of births was investigated.The JE patients who suffered from JE clinically at the age of 1-29, were more frequently born during the epidemic season of the epidemic years than what was expected from the seasonal birth frequencies of the general population. On the contrary, the number of JE patients born in the summer season of the non-epidemic years was nearly the same as expected from the general births in the same years. This may imply the possibility that the susceptibility to JE virus infection has been kept modified for many years by the inapparent infection of the JE virus in their fetal or neonatal stages.