Feasibility of achieving the 2025 WHO global tuberculosis targets in South Africa, China, and India: a combined analysis of 11 mathematical models

Abstract

Background: The post-2015 End TB Strategy proposes targets of 50% reduction in tuberculosis incidence and 75% reduction in mortality from tuberculosis by 2025. We aimed to assess whether these targets are feasible in three high-burden countries with contrasting epidemiology and previous programmatic achievements.

Methods: 11 independently developed mathematical models of tuberculosis transmission projected the epidemiological impact of currently available tuberculosis interventions for prevention, diagnosis, and treatment in China, India, and South Africa. Models were calibrated with data on tuberculosis incidence and mortality in 2012. Representatives from national tuberculosis programmes and the advocacy community provided distinct country-specific intervention scenarios, which included screening for symptoms, active case finding, and preventive therapy.

Findings: Aggressive scale-up of any single intervention scenario could not achieve the post-2015 End TB Strategy targets in any country. However, the models projected that, in the South Africa national tuberculosis programme scenario, a combination of continuous isoniazid preventive therapy for individuals on antiretroviral therapy, expanded facility-based screening for symptoms of tuberculosis at health centres, and improved tuberculosis care could achieve a 55% reduction in incidence (range 31-62%) and a 72% reduction in mortality (range 64-82%) compared with 2015 levels. For India, and particularly for China, full scale-up of all interventions in tuberculosis-programme performance fell short of the 2025 targets, despite preventing a cumulative 3·4 million cases. The advocacy scenarios illustrated the high impact of detecting and treating latent tuberculosis.

Interpretation: Major reductions in tuberculosis burden seem possible with current interventions. However, additional interventions, adapted to country-specific tuberculosis epidemiology and health systems, are needed to reach the post-2015 End TB Strategy targets at country level.

Funding: Bill and Melinda Gates Foundation.

Figure 1

TB Care and Prevention framework The patient care pathway from disease to completion of treatment (blue boxes and arrows). Areas affected for enhancing current tuberculosis programme activities (ie, intervention scenarios) are shown in grey boxes and arrows, with the number (#x) to link them to activities in table 2 and the appendix section 3.

Figure 2

Baseline calibration and projections for China, India, and South Africa Y-axes scales have different values. Coloured lines show model results, black dots and lines show required calibration ranges. Additional calibration targets included prevalence surveys (China, 2000 and 2010) and 2–5% annual decline in incidence (South Africa). See appendix section 1 and 4 for details.

Figure 3

Impact of interventions on incidence for national tuberculosis programmes and advocacy scenarios Figure shows the impact of baseline (left of dotted line) and incremental (excluding baseline, right of dotted line) impact of individual intervention scenarios (triangles and circles). Lines between models are for illustration of within-model impact of interventions. Models had to reflect the activities as provided by scenario setters (see table 2) as best as possible within their model framework, and provide an implementation narrative (see appendix section 3). Inevitably, simplification will have occurred to fit the intervention within the model structure. For example, in South Africa, the method of implementing the intervention scenario of isoniazid preventive therapy for HIV positive individuals receiving antiretroviral therapy will depend on whether the model had a separate compartment for isoniazid preventive therapy to track the number of individuals who were screened (as part of annual re-screening for tuberculosis) and have separate tuberculosis progression rates. See appendix section 3 for guidance and specific implementation.

Figure 4

Combination intervention impact on incidence and mortality in scnearios for national tuberculosis programmes (top row) and advocacy (bottom row) Figure shows individual model impact (triangles and circles) and median impact (black bars). Dotted lines show 2025 milestones of 50% reduction in incidence (left column) and 75% reduction in mortality (right column).