The impact of active case finding on transmission dynamics of tuberculosis: A modelling study

Abstract

Background In the last decade, active case finding (ACF) strategies for tuberculosis (TB) have been implemented in many diverse settings, with some showing large increases in case detection and reporting at the sub-national level. There have also been several studies which seek to provide evidence for the benefits of ACF to individuals and communities in the broader context. However, there remains no quantification of the impact of ACF with regards to reducing the burden of transmission. We sought to address this knowledge gap and quantify the potential impact of active case finding on reducing transmission of TB at the national scale and further, to determine the intensification of intervention efforts required to bring the reproduction number (R0) below 1 for TB. Methods We adopt a dynamic transmission model that incorporates heterogeneity in risk to TB to assess the impact of an ACF programme (IMPACT TB) on reducing TB incidence in Vietnam and Nepal. We fit the models to country-level incidence data using a Bayesian Markov Chain Monte Carlo approach. We assess the impact of ACF using a parameter in our model, which we term the treatment success rate. Using programmatic data, we estimate how much this parameter has increased as a result of IMPACT TB in the implementation districts of Vietnam and Nepal and quantify additional efforts needed to eliminate transmission of TB in these countries by 2035. Results Extending the IMPACT TB programme to national coverage would lead to moderate decreases in TB incidence and would not be enough to interrupt transmission by 2035. Decreasing transmission sufficiently to bring the reproduction number (R0) below 1, would require a further intensification of current efforts, even at the sub-national level. Conclusions Active case finding programmes are effective in reducing TB in the short term. However, interruption of transmission in high-burden countries, like Vietnam and Nepal, will require comprehensive incremental efforts. Complementary measures to reduce progression from infection to disease, and reactivation of latent infection, are needed to meet the WHO End TB incidence targets.

Community-based COVID-19 active case finding and rapid response in the Democratic Republic of the Congo: Improving case detection and response

“…According to the WHO, two important community-based interventions that can help reduce the burden of neglected tropical diseases are the implementation of ACF campaigns and mass prophylaxis [ 22 ]. Furthermore, the WHO demonstrated that the ACF program is effective in reducing TB in the short term and can substantially reduce patient-incurred costs, which contribute to the end-TB strategy target [ 23 , 24 ].…”

The impact of a combined TB/HIV intervention on the incidence of TB infection among adolescents and young adults in the HPTN 071 (PopART) trial communities in Zambia and South Africa

“…Little is known about the best timing to efficiently measure the impact on TB-infection rates after an intervention has been introduced. Modelling studies on active case finding suggest it might take several years before the impact is noticeable [36]. In our study, the cohort of AYA was enrolled approximately 18 months after the PopART intervention (that was delivered for four years) ended.…”