Studies on Japanese Encephalitis in Hyogo Prefecture in the Recent Three Years

I. Epidemiology and the Complement Fixation Tests with Patients' Sera

Abstract

Japanese encephalitis was diagnosed clinically in 132 patients, including 74 males and 58 females, in Hyogo Prefecture in the 3 years from 1953 to 1955. The epidemic began in June or July, reached its peak from the end of August to September and subsided practically in October. The age distribution was characterized by the predominance of children and young patients under 20, which was followed by the older patients over 50. Those between 21 and 50 of age were the least affected. The average case mortality rate ranged from 40 to 50%. The mortality rate was slightly higher in the female than in the male, and higher in adults than in children. In mortal cases the death occurred relatively early, within 10 days after the onset of the disease.
The serum could be obtained from 82 patients, and was examined for the complement fixation reaction of Japanese encephalitis. A positive reaction was confirmed with 29 (72.5%) out of 40 patients, whose blood could be examined not only at the initial stage of the disease, but also repeatedly thereafter with an interval of 7-10 days. On the other hand, only 6 (14.2%) out of 42 patients gave a positive reaction, whose blood examination was performed only once and within a week after the onset of the disease. The complement fixation reaction with the sera of encephalitis patients was negative in the great majority of cases up to the 7th day of disease, and turned to positive as a rule after the 8th day. The highest fiter of antibody was reached generally in about two weeks after the beginning of the disease.