A climatologic analysis of human rotavirus infection in inpatients with acute diarrhea was conducted over a seven-year period. The infection frequency appeared to be related to temperature, but not to relative humidity. Human rotavirus infection was found to appear abruptly when the mean temperature of any 10-day period became less than 5 C (November or December), reached a peak when it was less than 0 C (January and February), and waned when it became greater than 20 C (June and July) in the city of Yamagata in northern Japan.

Five hundred eighty-seven adenovirus type 3 (Ad3) isolates were established from children with acute respiratory infections (ARI) from 1986 to 1991, in Yamagata, Japan. Ad3 could be found in almost all the months during the 6 years when two epidemics occurred, in 1987 and 1989. A molecular epidemiological study was done on 346 of the 587 isolates, using restriction endonucleases; BamHI, HindIII, SmaI, and BgIII were used. The Ad3 isolates were classified into seven genome types. The genetic differences among the seven genome types were < 0.9%, and their phylogenetic tree, estimated by the neighbor-joining method, correlated highly with their monthly distribution. One genome type predominated for 56 months, while the other six related genome types cocirculated for a short period. These results suggested that the predominant genome type of Ad3 might have been endemically perpetuated in the Yamagata area with minor genomic variations. Furthermore, the outbreaks of Ad3 may have been due not to the appearance of a new genome type but rather to the endemic genome type.

The RNA of strains of rotavirus obtained from patients hospitalized with diarrhea during two winter epidemics of rotaviral infection in successive years (November 1981 through April 1982 and December 1982 through April 1983) was analyzed by polyacrylamide gel electrophoresis. A single dominant electropherotype was found during the first two or three months of each epidemic. In contrast, various electropherotypes were identified during the latter portion of each epidemic. RNA patterns of the rotaviral strains that were dominant during the early phase of the two epidemics were different from each other.

Using human embryonic fibroblast (HEF) and HEp-2 cell cultures, adenoviruses were isolated from 989 (3.7%) out of 26,793 pediatic patients with ART in Yamagata, Japan from January, 1986 to December, 1991. All isolates were identified as types 1 (Adl)-6 and no other serotypes were identified. Epidemiologic feature was different depending on the subgenus group. Adl, 2,5 and 6 (group C) were endemic and the infections occurred frequently in the summer season. Ad3 (group B) was epidemic in the autumn to winter season, although the virus was isolated every month in non-epidemic season. No seasonal distribution of Ad4 (group E) could be determined because the number of patients was limited. Neutralizing antibody positive ratio for group C were more than 40% at 1-2 years of age and almost 100% by 10 years of age but those for Ad3 (group B) were 40% by 10 years of age. The neutralizing antibodies for Ad4 (group E) or Adz (group B) became negative by 10 years of age. With group C infections, most cases were infants and young children less than 2 years of age, but Ad3 infections were older children with the peak at 4 and 5 years of age.adenovirus; epidemiology; acute respiratory infections