The long-term impacts of domestic and international TB service improvements on TB trends within the United States: a mathematical modelling study
Authors: Menzies Nicolas A , Swartwood Nicole A , Cohen Ted , Marks Suzanne M , Maloney Susan A , Chappelle Courtney , Miller Jeffrey W , Asay Garrett R Beeler , Date Anand A , Horsburgh C Robert , Salomon Joshua A 
Published: March 2024

Background

For low TB incidence settings, disease elimination is a long-term goal. We investigated pathways to TB pre-elimination and elimination (incidence <1.0 and <0.1 per 100,000, respectively) in the United States.

Methods

Using a mathematical modelling framework, we simulated how U.S. TB incidence could be affected by changes in TB services in the countries of origin for future migrants to the United States, as well as changes in TB services inside the United States. We constructed intervention scenarios representing improvements in TB services internationally and within the United States, individually and in combination, plus a base-case scenario representing continuation of current services. We simulated health and economic outcomes until 2100.

Findings

Under the base-case, U.S. TB incidence rates were projected to decline to 1.8 (95% uncertainty interval: 1.5, 2.1) per 100,000 by 2050. Intervention scenarios produced substantial reductions in TB incidence, with the combination of all domestic and international interventions projected to achieve pre-elimination by 2033 (2031, 2037). Compared to the base-case, this combination could avert 101 (84, 120) thousand U.S. TB cases and 13 (11, 16) thousand U.S. TB deaths over 2025-2050; the total economic value of these TB incidence reductions was estimated as US$68 (33, 112) billion. TB elimination was not projected before 2100.

Interpretation

Strengthening TB services domestically, promoting the development of more effective technologies and interventions, and supporting TB programs in high-burden countries are key strategies for accelerating progress towards TB elimination in the United States.

Funding

U.S. Centers for Disease Control and Prevention.

Research in Context

Evidence before this study

A number of studies have investigated the potential health impacts of tuberculosis intervention options in individual countries, across high incidence and low incidence settings. Studies in high incidence settings have generally emphasized TB case detection as a high-impact strategy, while studies in low incidence settings have focused on preventive treatment among individuals with TB infection. Few studies have examined the combined effect of interventions choices in both high- and low-incidence settings, and how these choices can contribute to progress towards TB elimination goals in individual countries.

Added value of this study

Using a mathematical modelling approach, this study assessed how interventions in high burden countries and interventions used within the United States could affect future TB trends within the United States. Dependencies between different TB epidemics were modelled explicitly through migration. The analysis examined the extent to which different intervention combinations could accelerate progress towards TB pre-elimination and elimination goals (incidence <1.0 and <0.1 per 100,000, respectively).

Implications of all the available evidence

In this low-burden setting, actions to strengthen TB services domestically, promote the development of more effective technologies and interventions, and support TB programs in high-burden countries were all found to be complementary and impactful strategies for accelerating progress towards TB elimination.