Sero-Epidemiological Study of Japanese Encephalitis with Special Reference to the Problem of Familial Aggregation

Abstract

In order to elucidate the epidemiology of Japanese Encephalitis, the complement fixation tests (C.F.T.) have been continuously carried ouf on nearly all inhabitants of arural village: 862 persons in Toyama Prefecture in Japan, at 3 to 5 months intervals during the period from November 1951 to February 1954.
In this paper detailed statistical studies are focused on the problem of the familial aggregation of C.F.T. positive reactors. The steps of the study were as follows. (a) Calculation of the distribution of positive reactors in a family by number of family members. (b) Computation of the expected frequencies from the binominal distribution. (c) X²-test in order to examine the significance of the difference between the actual and expected frequencies.
These methods of statistical study were applied firstly to the whole tested persons, then to the positive reactor distribution by the number of family members, the sex and the age of the persons and by the district and the time of the tests and at last to the distribution of positive convertors in each period by number of family members.
As the common results of these studies made from various angles, it is noted that expected frequencies fit very closely to the actual frequencies.
The fact indicates directly that the subclinical infection of Japanese Encephalitis does not aggregate in a family and consequently the mode of spread of the infection seems to belong to that of common vehicles and not to that of from person to person.