Migration-linked tuberculosis epidemics: how the future of tuberculosis in high-income countries will depend on the success or failure of TB control in high-burden settings.

BackgroundGlobally, Mycobacterium tuberculosis (Mtb) is the leading cause of death due to a single pathogen, with most tuberculosis cases occurring in low- and middle-income countries. A growing proportion of tuberculosis cases in high-income countries occur among foreign-born individuals, often resulting from a Mtb infection acquired before migration. As a result, tuberculosis trends in many high-income countries are increasingly influenced by tuberculosis epidemiology in and migration patterns from other countries. Our objective was to estimate how the future risks of tuberculosis in high-income countries will change depending on the success or failure of efforts to combat tuberculosis in high-burden settings. MethodsWe defined scenarios representing different levels of optimism regarding tuberculosis control in high-burden settings. The most optimistic scenario assumed high-burden countries would achieve tuberculosis elimination targets proposed by the WHO. The most pessimistic assumed major increases in tuberculosis following sharp reductions in international health aid. A base-case scenario assumed continuation of pre-2025 trends. We used calibrated mathematical models to predict how these scenarios would change Mtb infection prevalence among future migrants and thereby affect tuberculosis incidence and deaths in high-income countries. We considered 49 high-burden countries (as defined by the WHO), and projected tuberculosis outcomes in 60 high-income countries until 2050. FindingsOver 2025-2050, we project there will be 2,266,000 (95% credible interval (CI): 1,938,000-2,744,000) tuberculosis cases in high-income countries if pre-2025 trends continue, with 57% (95%CI: 50-65) of these cases occurring among foreign-born individuals (up from 39% in 2024), for an average incidence rate of 6.5 (95%CI: 5.3-8.3) per 100,000 in 2050. Under the most optimistic scenario we estimated that there would be 785,000 (95%CI: 647,000-950,000) fewer tuberculosis cases and 63,000 (95%CI: 52,000-78,000) fewer tuberculosis deaths in high-income countries over 2025-2050, with an incidence of 2.3 (95%CI: 1.8-3.0) per 100,000 in 2050. Under the most pessimistic scenario, we estimated there would be 1,168,000 (95%CI: 983,000-1,324,000) additional tuberculosis cases and 95,000 (95%CI: 83,000-106,000) additional tuberculosis deaths in high-income countries over 2025-2050, with incidence of 11.5 (95%CI: 9.5-14.0) per 100,000 in 2050. The United States, United Kingdom, Germany, France, and Italy were projected to be the most affected high-income countries. InterpretationFor high-income countries, the future risks of tuberculosis incidence and mortality could vary by as much as 5-times depending on the success or failure of tuberculosis control in high-burden settings, fundamentally shaping the strategies required to prevent, detect and treat tuberculosis in these settings.