• Kawasaki disease
• epidemiology
• public health

Using epidemiological investigation to characterise a disease in space and time can be a powerful tool to generate hypotheses about aetiology. Reports from Japan1 and the UK2 underscore the distinct seasonality of Kawasaki disease (KD) in two geographically distant regions of the northern hemisphere. The reports also document an increasing incidence of KD over time. While the seasonality of KD both in Japan and globally has been previously well documented, further analyses of patient characteristics and outcomes by season are yielding a more granular picture of the interaction between the environment and clinical features.3–5

In the report by Shimizu and colleagues1, the authors analysed 744 patients admitted to six hospitals in a single metropolitan region in Japan. Although details of the completeness of the reporting are lacking, this type of regional analysis may be more complete than the nationwide KD surveys in Japan that have an ~75% response rate. In addition, the authors had access to more detailed clinical information than is …