An ecological study of tuberculosis transmission in California

Objectives. We evaluated the association between ecological factors and rates of tuberculosis within California, using pediatric tuberculosis as an indicator of new transmission. Methods. Ecological variables such as racial/ethnic distribution, immigration level, education, employment, poverty, and crowding were obtained from the United States Census for each census tract in California. These data were incorporated into a negative binomial regression model with the rate of pediatric tuberculosis disease in each census tract as an outcome variable. Disease rates were obtained by geocoding reported cases. Subsections of the state (San Francisco and Los Angeles) were examined independently. Results. Census tracts with lower median incomes, more racial/ethnic minorities, and more immigrants had higher rates of pediatric tuberculosis. Other frequently cited risk factors such as overcrowding and unemployment were not associated with increased disease after adjusting for other measures. Risks were comparable across regions, but subtle differences were noted. Conclusions. The techniques used in this work provide a way to examine a disease within its social context. The results confirmed that tuberculosis in California continues to be a disease of poverty and racial/ethnic minorities.