This dissertation examines the relationships between immigration and the incidence of tuberculosis (TB) disease and prevalence of TB infection in California and in the United States (U.S.). The majority of TB cases in California occur among foreign-born persons from countries with high TB burdens. Although the incidence of TB is declining, the decline among immigrants has stalled, and relationships of this trend with changes in immigration patterns are not well characterized. Census data suggest that immigration to California has undergone notable transitions since the 1990s that have shaped the volume, demographic and socioeconomic composition of immigration streams to the state. The first two papers of this dissertation explore the relationships between changes in immigration and the incidence of TB using the decomposition method, and an innovative application of cohort analysis. The third paper examines the only nationally representative survey of new immigrants in the U.S. to determine gaps in TB screening and to assess the prevalence and risk of latent TB infection (LTBI) in immigrant subgroups by country of origin. This unique data source allowed for the assessment of important immigration, health, and socioeconomic variables.

The decomposition of the recent decline in the incidence of TB among the foreign-born in California shows that changes in the population composition associated with immigration shifts made a modest contribution to the decline, with the majority of the decline due to group-specific declines in rates. There was a notable difference between Hispanics/Latinos and Asians/Pacific Islanders, whereby the impact of immigration shifts was much greater in the former group. The cohort analysis shows that waves of immigration have had varying impacts on the incidence of TB in California, some cohorts contributing to increasing incidence, and others to decreasing incidence. This suggests that the slowing in the decline of the incidence of TB may be due, in part, to immigration cohort entry effects. Identifying cohorts with elevated risk of TB can help develop and test hypotheses on the epidemiologic reasons for the observed effects, and can provide an evidence base for selecting demographic subgroups in which to prioritize TB screening. The TB screening uptake and TB prevalence analysis confirmed gaps in testing for TB that varied significantly by country of origin. Substantial variation in the prevalence and risk of LTBI was also found, which may inform public health efforts to prioritize the targeted testing and treatment to specific subgroups of highest risk.