The Prevalence of Tuberculosis Infection Among Foreign-Born Canadians: A Modelling Study

Abstract Background The prevalence of tuberculosis infection (TBI) is critical to designing tuberculosis (TB) prevention strategies, yet it is unknown in Canada. We estimated TBI prevalence among foreign-born Canadians. Methods Using a previously developed Gaussian process regression model, annual risk of infection trends abroad were constructed and used to estimate TBI prevalence by age and year of migration to Canada for persons from each of 168 countries. These stratified TBI prevalence estimates were combined with Canadian census data to estimate overall TBI prevalence among foreign-born residents during census years 2001, 2006, 2011, and 2016. We also estimated TBI prevalence according to age, WHO-estimated TB incidence in country of origin, and province/territory of residence. Finally, we estimated the prevalence of TBI acquired within the two preceding years. Results Estimated TBI prevalence among foreign-born Canadians overall was 25% (95% uncertainty interval [UI]: 20-35%), 24% (20-33%), 23% (19-30%), and 22% (19-28%) for census years 2001, 2006, 2011, and 2016, respectively. TBI prevalence increased with age at migration and TB incidence in the country of origin. In 2016, estimated TBI prevalence was lowest in Quebec (19%, 95% UI: 16-25) and highest in Alberta and British Columbia, at 24% each. Among all foreign-born Canadian residents with TBI in 2016, we estimated that only 1 in 440 were infected within the two preceding years. Interpretation Approximately 1 in 4 foreign-born Canadians has TBI; estimated prevalence has remained quite stable over the last two decades. However, a very small minority of people with TBI were infected within the last two years—the highest risk period for progression to TB disease. These data may inform future TBI screening policies.