Modelling tuberculosis transmission dynamics in Malaysia

Tuberculosis (TB) remains a major global public health challenge requiring urgent interventions to achieve the World Health Organization (WHO) End TB Strategy targets. This study aimed to develop and validate a compartmental model to estimate the TB reproduction number (R₀) and TB incidence in Malaysia, identify parameters influencing R₀ and TB incidence, and simulate TB incidence using baseline and intervention scenarios to 2035 to assess compatibility with achieving the WHO End TB Strategy target.

A Susceptible-Latent Fast-Latent Slow-Infectious-Recovered (SL_FL_SIR) compartmental model was developed and calibrated using national TB data from 2013 to 2023. Model calibration was performed using initial Monte Carlo exploration followed by Particle Swarm Optimisation to identify final calibrated parameters. R₀ was estimated using the next-generation matrix approach. Uncertainty was quantified using parametric bootstrapping with negative binomial observation model. Model validation used observed TB cases in 2024 and 2025 and was assessed using performance metrics. Global sensitivity analysis using Latin Hypercube Sampling and Partial Rank Correlation Coefficients identified parameters influencing R₀ and simulated TB incidence in 2035. TB incidence scenarios were simulated to 2035 by varying the transmission rate (β), rate of progression from active TB to recovery (γ), and rate of progression from latent fast to active TB (ε).

The calibrated model-estimated TB cases and incidence showed good fit to observed TB cases and incidence during calibration and short-term validation periods, with satisfactory performance metrics. The estimated R₀ was 1.09 (95% CI: 1.01-1.27). Parameters influencing R₀ were β and γ, while parameters influencing simulated TB incidence in 2035 were β, γ, and rate of progression from latent slow to active TB (κ). TB incidence showed minimal reduction by 2035 in the baseline scenario. The most intensive intervention scenario reduced TB incidence by 66.21% by 2035, relative to 2015.

The SL_FL_SIR model showed that TB transmission in Malaysia remains self-sustaining, with estimated R₀ slightly above 1. Although combined TB-specific interventions could reduce simulated TB incidence, achieving the WHO End TB Strategy targets by 2035 will likely require integrated TB control with broader improvements in population health and social determinants of TB risk.