EPIDEMIOLOGIC OBSERVATION ON OUTBREAKS OF ASEPTIC MENINGITIS DUE TO ECHO VIRUS 4 IN TOYAMA PREFECTURE 1964

Two cases of aseptic meningitis epidemic were observed at Toyama City and Fuchu Town from July to September, 1964. Many Japanese reports described this disease at that time indicated that similar epidemics of aseptic meningitis have been found in many districts of Japan in 1964 and 1965. We examined above our cases by the epidemiological and virological procedures. Results obtained are summarized as follows:1) The peak of outbreaks in Toyama City case, total 29 patients, lasted for 2 months was not clear, but it was found on the fifth week of July or on the first week of August in Fuchu Town case, total 41 patients, similarly retained for 2 months.2) The age distribution of patients, in which 67.1 per cent was shown to be accumulated in 5 to 9 years old, ranged from 12 months to 13 years old.3) In 25 cases out of 51 patients tested in both epidemics the ECHO-4 virus was recovered, including 3 cases, from those spinal fluids viruses were isolated.4) The neutralizing antibody responses in paired sera of 26 patients tested against ECHO-4 virus were proved to be significant using DuToit strain of virus and continuous GMK cell line, though the acute phase sera of 3 cases had already shown positive antibody titers in 1:16.5) Serological investigations on possible occurrence of ECHO-4 virus infection at Toyama area were performed by the similar procedures to those as in 4). Human sera collected voluntarily at Horioka Town for such purpose were grouped as each 70 samples obtained before and after aseptic meningitis outbreaks in 1964. The antibody possessing ratio in the sera of children under 9 years old was only 3 per cent in the grouped sera collected in 1963 before epidemics of aseptic meningitis. Contrary to this low ratio, higher positive ratio of more than 50 per cent, was observed in the sera of the same ages group taken in 1964 after outbreaks of this disease.6) From these serological results considering antibody almost negative age group under 9 years old it may be assumed that the aseptic meningitis epidemics caused by ECHO-4 virus had not occurred in infants or children at Toyama area during past 9 years up to 1963.