Relationship of climate, ethnicity and socioeconomic status to Kawasaki disease in San Diego County, 1994 through 1998

Background. Kawasaki disease (KD) is the most common cause of acquired hear t disease in children in the United States, By monitoring trends in patient numbers and demographics during a 5-year period, we were able to explore t he relation ship between climate, ethnicity, socioeconomic status and susce ptibility to KD. Methods. We conducted active surveillance for all patients hospitalized wit h KD in San Diego County from 1994 through 1998, Data on seasonal variation in monthly rainfall and temperature were obtained from the US Meteorologic al Service. Patient sex, age, date of admission and self-reported ethnicity were identified from patient medical records. Socioeconomic status was ass essed on the basis of insurance status among patients hospitalized at a sin gle institution. Results. During the 5-year period there were 169 cases of KD in San Diego C ounty. The overall annual incidence of KD in children <5 years of age range d from 8.0 to 15.4/100 000, KD incidence was inversely associated with aver age monthly temperature (r = -0.,47, P < 0.001) and positively associated w ith average monthly precipitation (r = -0.52, P <0.001), Asian/Pacific Isla nders <5 years of age were 2.7 times as likely and Hispanics were one-third as likely to be hospitalized for KD than children from all other ethnic gr oups combined. Children with private or military insurance in all ethnic gr oups were more likely to have a diagnosis of KD than children with governme nt assistance or no insurance. After controlling for insurance status, only Asian/Pacific Islanders remained at increased risk (rate ratio, 2.14) for KD relative to all other ethnic groups conibined. Conclusion, KD is a common childhood vasculitis of unknown etiology. The sk ewed ethnic distribution and seasonality are consistent with the hypothesis that KD is an infectious disease that is influenced by environmental and g enetic factors.