Country-specific intervention strategies for top three TB burden countries using mathematical model

Abstract

Tuberculosis (TB) is one of the top 10 causes of death globally and the leading cause of death by a single infectious pathogen. The World Health Organization (WHO) has declared the End TB Strategy, which targets a 90% reduction in the incidence rate by the year 2035 compared to the level in the year 2015. In this work, a TB model is considered to understand the transmission dynamics in the top three TB burden countries-India, China, and Indonesia. Country-specific epidemiological parameters were identified using data reported by the WHO. If India and Indonesia succeed in enhancing their treatment protocols and increase treatment and treatment success rate to that of China, the incidence rate could be reduced by 65.99% and 68.49%, respectively, by the end of 2035. Evidently, complementary interventions are essential to achieve the WHO target. Our analytical approach utilizes optimal control theory to obtain time-dependent nonpharmaceutical and latent case finding controls. The objective functional of the optimal control problem includes a payoff term reflecting the goal set by WHO. Appropriate combinations of control strategies are investigated. Based on the results, gradual enhancement and continuous implementation of intervention measures are recommended in each country.

Fig 1. Flow diagram of TB dynamic model.

Fig 2. Total population data and the best fit of N(t) for India (left), China (middle), and Indonesia (right).

Fig 3. Reported numbers of incident cases (circle) and corresponding best fitted curves of κE(t) (solid) in top three TB burden countries.

Fig 4. Expected number of incident cases (left) and incidence rate (right) from the TB model.

Fig 5. C3: Constant case holding and active case finding control strategies in India and Indonesia.

The likely percentage reductions in the TB incidence rate are 65.99% and 68.49% in India and Indonesia, respectively. Note that no control strategy is applied in China.

Fig 6. Scenario 1: Nonpharmaceutical control strategy.

Optimal control strategies with constant case holding and active case finding controls (dash-dotted) or without the two constant controls (solid) are displayed as functions of time, in the frames on the left. The frames on the right present the corresponding incidence rates and the WHO targets in 2035 (black dashed line).

Fig 7. Scenario 2: Latent case finding control strategy.

Optimal control strategies with constant case holding and active case finding controls (dash-dotted) or without the two constant controls (solid) are displayed as functions of time in the left frames. The right frames show the corresponding incidence rates and the WHO 2035 targets (black dashed line).

Fig 8. Scenario 3: Coupled control strategy.

The left frames depict optimal control strategies with constant case holding and active case finding controls (dash-dotted) or without the two constant controls (solid), as functions of time. The right frames show the corresponding incidence rates and the WHO targets in 2035 (black dashed line).