Abstract：
During the coronavirus disease 2019 (COVID-19) pandemic, known viral diseases declined in all ages. By using the current situation as a natural experiment, this study aimed to evaluate whether the change in the incidence of Kawasaki disease (KD) during the COVID-19 pandemic varies with age and whether a specific infectious disease mediates the occurrence of KD. Monthly number of KD patients were extracted from the nationwide inpatient database. Segmented regression analysis was conducted on the interrupted time series data. Additionally, causal mediation analysis was performed to examine the role of viral infections in the changes in the number of KD patients. After the first emergency declaration for COVID-19 in Japan, there was an immediate decrease in the number of KD patients per 100 000 population aged between 6 months and 4 years (immediate change = -2.66; 95% confidence interval [CI]: -5.16 to -0.16) and aged 5-15 years (immediate change = -0.26; 95% CI: -0.49 to -0.04). However, no immediate change was observed in patients under 6 months of age. In the causal mediation analysis for each viral infection, it was found that the decrease in the number of patients with KD was mediated by changes in the number of patients with pharyngoconjunctival fever and infectious gastroenteritis. The current results suggest that viral infections may be one of the etiological agents for KD, while they may not be the main cause in early infancy. Specifically, we found that adenovirus infection and gastroenteritis was closely related to the onset of KD in some areas of Japan.
摘要：
在2019年冠状病毒病（COVID-19）大流行期间，已知的病毒性疾病在所有年龄段都有所下降。通过将当前情况作为自然实验，本研究旨在评估COVID-19大流行期间川崎病(KD)发病率的变化是否随年龄而变化,以及特定传染病是否介导KD的发生.从全国住院患者数据库中提取KD患者的每月数量。对中断的时间序列数据进行分段回归分析。此外,我们进行了因果中介分析,以检查病毒感染在KD患者数量变化中的作用.在日本首次发布COVID-19紧急声明后，年龄在6个月至4岁(即时变化=-2.66;95%置信区间[CI]:-5.16~-0.16)和5~15岁(即时变化=-0.26;95%CI:-0.49~-0.04)的每10万人口中KD患者的数量立即减少.然而,在6月龄以下的患者中未观察到即时变化.在每种病毒感染的因果中介分析中，发现KD患者数量的减少是由咽结膜热和感染性胃肠炎患者数量的变化介导的。目前的结果表明，病毒感染可能是KD的病因之一，虽然它们可能不是婴儿期早期的主要原因。具体来说,我们发现腺病毒感染和胃肠炎与日本某些地区KD的发病密切相关。
