Epidemiologic characteristics of children hospitalized for Kawasaki disease in California

Objective. To evaluate the epidemiologic pattern of Kawasaki disease (KD) in California. Methods. Statewide hospital discharge data from California from 1995 through 1999 were used. Children 0 through 17 years old who had a discharge diagnosis of KD (by ICD9-CM code 446.1) were identified. Precipitation and temperature data of climate divisions of the state were used to determine their possible association with incidences of KD. Multiple regression analysis was performed to evaluate factors related to the KD incidence of the counties. Results. There were 2325 patients admitted to 194 California hospitals during the 5-year study period. The male-to-female ratio was 1.62. Median age was 30 months; peak incidence by year of age was in the second year of life. Overall annual incidence was 15.3 cases per 100 000 children <5 years old and 3.2 cases per 100 000 children 5 through 9 years old. Compared with 1995 and 1996, the incidence for children <5 years old increased by 30% in 1997 and 1998 (P < 0.01). In contrast the incidence for children 5 through 9 years old remained relatively unchanged. Asians had the highest incidence of 35.3 cases per 100 000 children <5 years old, followed by blacks (24.6) and whites (14.7) (P < 0.01). The number of cases peaked in March and had its nadir in September. In a multiple regression analysis, no association was found between KD incidence and temperature or precipitation. KD incidence was not related to average family size, proportion of Asians in the population, population density or whether the county is in northern or southern California. There was no in hospital death. The median length of hospital stay was 2 days. Conclusions. The incidence of Kawasaki disease in patients <5 years old increased in 1997 and 1998. Asians had the highest KD incidence compared with other races. Peak incidence was in March, and the lowest incidence was in September. KD incidence was not associated with temperature, precipitation, family size or population density.