During July to December in 1991, an epidemic of aseptic meningitis occurred in Gifu Prefecture in children. Epidemiological, virological and serological investigations were performed. The results are as follows:
1) Cases involved ranged from 0 to 13 years of age, and 75.9% of them were in the 3 to 7 year of age group.
2) Three types of enteroviruses were isolated from 83 of 133 cases (62.4%), and the echovirus type 30 was recovered from 71 cases (85.5%).
3) In 1991 with the cross neutralizing test between the prototype and isolated strains of echovirus type 30, a remarkable antigenic variation could not be found.
4) In serological studies, the positive rates of neutralizing antibodies to echovirus type 30 in infant sera aged 0-9 years in 1992-1993, was 51.9% with the prototype strain, but 34.0% with an isolated strain in 1991.