Hospitalizations for Kawasaki disease among children in the United States, 1988-1997.

OBJECTIVE: To evaluate the epidemiologic pattern of Kawasaki disease (KD) in the United States over 10 years.
METHODS: The National Inpatient Sample, a stratified national sample of >900 hospitals in 22 states of the United States, was used. Data on hospital discharges from 1988-1997 were analyzed. Patients <18 years of age with a discharge diagnosis of KD were identified.
RESULTS: There were 6442 patients with KD admitted to 651 hospitals. Median age at hospital admission was 2 years. Peak incidence by year of age was 1 year old. Children <2 years old accounted for 36.6% of all cases; <5 years old, 75.6%; and <10 years old, 95.6%. The age distribution seems to be wider than reported from Japan. The incidence for children <5 years old was 8.1 per 100 000 people in 1988, and increased to 18.5 in 1997. There were 3905 males (60.6%) and 2537 females (39.4%), for a male-to-female ratio of 1.54. The incidences were higher in winter and spring (December to May) and dropped to a nadir between July and September. No apparent change in seasonal pattern was noted over 10 years. The South census region showed a seasonal change 2 to 3 months ahead of other regions. The overall in-hospital mortality rate was 0.17%. The mortality rate in children > or =10 years (1.4%) was significantly higher in than children <10 years (0.11%).
CONCLUSIONS: KD affects mainly children under 5 years of age, with a peak incidence in children 1 to 2 years of age. The incidence of KD was rising over the study period. There is a male predominance. Although KD occurs year-round, the lowest incidence is seen from July through September. Such seasonal variation did not change over the 10 years. Seasonal pattern may vary in different geographic regions. Mortality from KD is rare, although children > or =10 years are at higher risk.