Spatial and temporal clustering of Kawasaki syndrome cases

The etiology of Kawasaki syndrome (KS) remains unknown despite 30 years of intensive search for an agent. Epidemiologic clues to a possible infectious etiology include the seasonal distribution of cases, the previous occurrence of epidemics, the clinical features of the syndrome that mimic other infectious rash/fever illnesses in children, the self-limited nature of the illness, and the peak age incidence in the toddler years.

We examined the epidemiology and spatial and temporal distribution of KS cases in San Diego County, California during the 6-year period from 1998 to 2003. Clustering in space and time was analyzed using geo-referenced data with the K-function, the local G-statistic, and Knox statistic.

A total of 318 patients were identified through active surveillance. The overall annual incidence was 21.7/100,000 in children <5 years, with rates in whites, white Hispanics, and Asian/Pacific Islanders of 15.3, 20.2, and 45.9/100,000, respectively. The Knox test showed significant clustering of cases within the space-time interval of 3 km and 3-5 days.

This is the first study of KS cases to use geo-referenced point pattern analysis to detect spatial and temporal clustering of KS cases. These data suggest that an infectious agent triggers the immunologic cascade of KS.