ZAMSA TB Study

ZAMSA TB Study: Zambia, Malawi, South Africa Tuberculosis Study 

Advancing epidemiological methods for surveillance of Mycobacterium tuberculosis infection 

 Tuberculosis (TB) remains a major global health challenge, causing over 1.25 million deaths annually, more than any other infectious disease. TB transmission is increasingly concentrated in spatial hotspots and among vulnerable populations, particularly in urban and peri-urban areas. Effective public health strategies require real-time, sub-district surveillance to identify high-risk populations, allocate resources efficiently, and monitor progress over time. Given these shifting dynamics, there is a growing need to reconsider TB surveillance methodologies, as current approaches are inadequate.

The overall aim of the ZAMSA TB study, locally referred to as the Atontho study, is to develop and validate innovative epidemiological methods for understanding recent TB transmission through convenience serosampling of Mycobacterium tuberculosis (Mtb) immunoreactivity, thereby supporting the targeted deployment of interventions such as TB vaccines and measuring their impact during implementation. Funded by the Wellcome Trust, and conducted in collaboration with the University of Glasgow, the University of Cape Town, and the Malawi Liverpool Wellcome Project, the study will recruit children aged 1–5 years living in the Chipata and Kanyama catchment areas of Lusaka, along with children from Cape Town and Blantyre.

In Lusaka, a mixed-methods approach will be applied, consisting of three components: a cross-sectional study, a nested cohort study, and a qualitative study. In the cross-sectional study, convenience sampling-based IGRA testing will be conducted among young children attending healthcare facilities for non-illness-related reasons, complemented by geospatial mapping using the Electronic Participant Locator (ePaL). In parallel, random community-based sampling will be undertaken to validate the convenience sampling technique. Across the community and facility components combined, approximately 2,400 children will be recruited.

The nested cohort study will follow up IGRA-positive children, and a subset of IGRA-negative children, from the cross-sectional study for 12 months to determine reversion and conversion rates, providing calibration targets for prevalence-based modelled estimates. The qualitative study will explore barriers and facilitators to using the blood-based Mtb immunoreactivity surveillance among guardians and healthcare workers.

This study will provide a novel epidemiological framework to strengthen TB surveillance, enabling the identification of transmission hotspots and the design of more effective, targeted interventions and impact assessments. Its findings may have broader applications for other infectious disease control strategies. Finally, by testing young children for TB infection using IGRA and assessing them for TB disease, the study will facilitate early detection and linkage to appropriate care, ultimately contributing to improved paediatric TB control efforts.