EPIDEMICS OF ASEPTIC-MENINGITIS DUE TO ECHOVIRUS-30 IN JAPAN

Two rages of epidemic of aseptic meningitis (AM) due to echovirus 30 ( E30) in Japan were analyzed with respect to two sources of information , AM incidence and E30 isolation, both gathered through the National E pidemiological Surveillance of Infectious Diseases. The first E30 epid emic spread throughout Japan in 1983 and ceased within the year. The s econd epidemic, starting in 1989, continued for the three successive y ears, and in the last year, 1991, the total E30 reports numbered 4,061 , the largest number of a single virus type ever reported. Although th e epidemic showed temporal and geographical shift and lasted for one o r two years in some areas, most laboratories reported the largest numb er of E30 isolation in 1991, Among E30-yielding cases with clinical in formation during 1982-1992, the associating frequency with AM was as h igh as 82.5%. Other central nervous system involvements such as enceph alitis, myelitis, encephalomyelitis and/or paralysis were reported in 36 E30-yielding cases and their monthly and age distributions were dif ferent from those of AM cases. The proportion of such disease among E3 0-yielding cases (0.60%) was close to that of other enteroviruses (0.5 6%). During the epidemics, E30 was isolated more frequently from cereb rospinal fluid than was E4 or E9 which prevailed coincidentally. E30 w as most frequently isolated from cases of 4-7 years of age, sharing th e common characteristic pattern of age distribution with other enterov iral meningitis. E30-yielding cases, however, involved a large number of older age groups than those of other enterovirus infections, and th is tendency was the most pronounced in the first epidemic year, 1983. The contribution of these E30 epidemics on the yearly trend of clinica lly reported AM incidence and on the shift of its age distribution was also analyzed.