Migration ties future TB in rich countries to control in high-burden nations

Tuberculosis remains the world’s deadliest single-pathogen killer, driven mainly by infections of Mycobacterium tuberculosis ( Mtb ) in low- and middle-income countries. But in many wealthy nations the face of TB is changing: a growing share of cases now occur among people born abroad, often reflecting infections they acquired before migrating. That means trends in high-income countries are increasingly tied to what happens elsewhere. To explore how those links will shape future disease burden, a team led by Nicolas A. Menzies used mathematical models to project TB outcomes under different global scenarios. The researchers framed a set of possible futures for high-burden settings — from an optimistic pathway in which WHO elimination targets are met, to a pessimistic pathway where cuts in international health aid precipitate major setbacks, with a middle “base-case” reflecting pre-2025 trends. They then estimated how changes in infection prevalence among future migrants would feed into TB incidence and deaths in 60 high-income countries through 2050. The study highlights that the future of TB in wealthy countries cannot be separated from efforts to control the disease elsewhere.

To make those comparisons, Menzies and colleagues defined scenarios capturing different levels of optimism about TB control in 49 WHO-defined high-burden countries and projected outcomes in 60 high-income countries until 2050. They used calibrated mathematical models to predict how each scenario would change Mtb infection prevalence among future migrants and thereby affect tuberculosis incidence and mortality. Under the base-case — continuation of pre-2025 trends — the team projects 2,266,000 (95% credible interval (CI): 1,938,000–2,744,000) tuberculosis cases in high-income countries over 2025–2050, with 57% (95% CI: 50–65) of those cases among foreign-born individuals (up from 39% in 2024) and an average incidence of 6.5 (95% CI: 5.3–8.3) per 100,000 in 2050. If high-burden countries achieve WHO elimination targets, the most optimistic scenario would avoid an estimated 785,000 (95% CI: 647,000–950,000) cases and 63,000 (95% CI: 52,000–78,000) deaths in high-income countries over 2025–2050, lowering incidence to 2.3 (95% CI: 1.8–3.0) per 100,000 by 2050. By contrast, a pessimistic scenario tied to sharp reductions in international aid could add 1,168,000 (95% CI: 983,000–1,324,000) cases and 95,000 (95% CI: 83,000–106,000) deaths, with incidence rising to 11.5 (95% CI: 9.5–14.0) per 100,000. The United States, United Kingdom, Germany, France, and Italy were projected to be most affected.

The study’s headline message is straightforward but powerful: the trajectory of TB in high-income countries over the next quarter-century depends heavily on what happens in high-burden settings. Depending on how well TB control succeeds or fails elsewhere, incidence and mortality in wealthy countries could vary by as much as fivefold. That has practical implications for planning public health strategies: if global control improves, resources in high-income countries could focus more on prevention, targeted screening of high-risk groups, and treating latent infections among migrants. If control deteriorates, richer countries may face higher case loads, more deaths, and the need to expand detection, treatment capacity, and possibly policy attention to migration-related risks. The findings underscore that investing in TB control abroad is not only a humanitarian priority but also a strategic investment in domestic health security for high-income nations.