Temporal and geographical clustering of Kawasaki disease in Japan: 2007-2012

BackgroundSince 1987, no study has reported the municipal-level geographical clustering of Kawasaki disease (KD) in Japan. Therefore, the aim of the present study was to identify the temporal and municipal-level geographical clustering of KD. MethodsThe annual incidence rates of KD for each municipality were calculated using nationwide data from 73758 patients with KD (2007-2012). To determine whether temporal and municipal-level clustering existed, we calculated the correlations of the annual incidence rates for each municipality during the study years, and compared these rates with those of the adjacent municipalities. Spatial scanning analysis was used to identify the geographical clusters for each year, and the incidence rates in those clusters were compared with the rates in the surrounding region. ResultsThe annual national incidence rate of KD, adjusted for the prefecture-specific response rate, was 322.45 patients per 100000 children aged 0-4 years. The correlation between the annual incidence rates during 2 consecutive years was significantly positive (coefficients, 0.149-0.428). On spatial scanning analysis, the most likely clusters were in the Tokyo metropolitan area during 2007-2010 and 2012, and in Kumamoto prefecture during 2011. ConclusionKawasaki disease exhibits temporal and municipal-level clustering.