Robustness of temporal and spatiotemporal clustering of KD Cases in San Diego County. (A) The cluster size distribution of the construction shown in Fig. 1C. The number of clusters of with more than S cases are plotted against S. The result is compared with the corresponding curves obtained from a Monte Carlo simulation of synthetic time series that have the same average incidence and average seasonality as the San Diego KD time series, but for which there is no temporal structure apart from a regular seasonal pattern. The error bars are ±1 standard deviation. (B) Excess K statistic for spatiotemporal distribution of KD cases. Red indicates significant spatiotemporal clustering with p < 0.05, and yellow indicates 0.05 < p < 0.15.