How immigration affects the burden of tuberculosis among foreign-born Canadians: estimates with dynamic models

BackgroundDespite only comprising about a quarter of the total population of Canada, foreign-born individuals bear about three-quarters of the burden of active tuberculosis (TB) cases. New immigrants arriving in Canada are screened for active TB, but generally not for latent TB infection (LTBI); thus the burden of LTBI among foreign-born Canadians is not well understood. MethodsTo investigate the impact of immigration on the burden of TB among foreign-born Canadians, we develop an SEIR-compartment model that distinguishes between actively infected, latently infected, and uninfected individuals. Unknown parameters are calibrated to reports on the incidence and prevalence of active TB in Canada. We validate our model by comparing model computed quantities to other estimates of tuberculosis burden among foreign-born Canadians, including an estimate of the prevalence of LTBI among immigrants entering Canada. ResultsIf the profile and number of immigrants arriving into Canada in the next decade is similar to the past decade, our model predicts that among the foreign-born population, Canada will not meet the End TB 2035 goal of reducing incidence by 90% compared to 2015. In fact, Canada would still fail to meet the incidence goal if no new immigrants are allowed to enter, primarily due to the activation of foreign-born Canadians with LTBI. Author summaryOur model examines how immigration affects the burden of tuberculosis among foreign-born Canadians. We fit a compartment model to calibration data, then find a feasible parameter set based on validation data. We forecast the incidence of TB in 2035 and demonstrate that regardless of which WHO geographic region immigrants originate from, Canada will fail to meet the WHO End TBs 2035 incidence goal (90% less than 2015) among the foreign-born population.