Regional Variations in the Incidence of Rotavirus Hospitalization in Children Living in Defined Regions of Akita and Kyoto Prefectures, Japan

Abstract

SUMMARY: Variable incidence rates of rotavirus gastroenteritis hospitalizations have been reported in Japan. However, it is not known whether the observed regional differences were due to the real difference in the occurrence of severe disease or other causes. This study aimed to determine the incidence rates of rotavirus hospitalization among children aged ＜5 years in the Yuri district in Akita prefecture and the Nantan district in Kyoto prefecture between March 2012 and February 2013. During this period, rotavirus vaccine uptake rates were equally low in both regions. All specimens were evaluated using the standardized case definition, severity scores, and the same assays. There were 44 rotavirus cases (44z) among 101 acute gastroenteritis-related hospitalizations in the Yuri district with a catchment population of 3,853, and 18 rotavirus cases (47z) among 38 acute gastroenteritis-related hospitalizations in the Nantan district with a catchment population of 5,128. While the severity score at the time of the hospitalizations was 11 in both hospitals, the incidence rates in Akita and Kyoto were 11.7 (95z confidence interval [CI]: 8.5-15.6) and 3.9 (95z CI: 2.1-5.5) per 1,000 child-years, respectively. Thus, there was a real difference in the occurrence rate of severe rotavirus infections between the 2 regions.