The Association Between Meteorological Factors and Rotavirus Gastroenteritis Incidence in Japan: A Time-Series Analysis.

Introduction Rotavirus is the principal pathogen responsible for acute gastroenteritis and severe diarrhea in children worldwide and remains a significant public health threat. However, studies on the association between rotavirus gastroenteritis epidemics and meteorological factors in Japan are still scarce. In this study, we aimed to quantify the short-term effects of meteorological factors on the incidence of rotavirus gastroenteritis in Japan using advanced time-series modeling approaches. Methods We conducted a two-stage time-series analysis. In the first stage, a time-stratified case-crossover study was performed using conditional quasi-Poisson regression in conjunction with a distributed lag nonlinear model to assess the association between meteorological factors and the incidence of rotavirus gastroenteritis across all 47 Japanese prefectures from 2014 to 2019. A multivariate meta-analysis was subsequently used to pool associations at the national level. Results A total of 26,549 cases of rotavirus gastroenteritis were included in the study. Our analysis revealed that low mean temperature and reduced relative humidity were significantly associated with an increased incidence of rotavirus gastroenteritis. More specifically, the overall lag-cumulative relative risk (RR) of rotavirus gastroenteritis peaked at approximately 13.0°C (RR: 2.2, 95% confidence interval (CI): 1.9-2.6) relative to a reference mean temperature of 25°C. Similarly, the RR was maximized at a relative humidity of approximately 55% (RR = 1.7, 95% CI: 1.4-2.2) compared with 77%. Conclusions This nationwide study showed that cold and dry environmental conditions were associated with an elevated risk of rotavirus gastroenteritis, which varied markedly based on region.