Methodological Evaluation of Public Health Surveillance Systems in South Africa Using a Difference-in-Differences Model

Public health surveillance systems in South Africa have been established to monitor infectious diseases such as tuberculosis (TB). However, their effectiveness and impact on reducing disease prevalence are not well understood. A comprehensive search strategy was employed to identify relevant studies, focusing on those that used a difference-in-differences (DiD) approach to measure risk reduction attributable to surveillance systems. Studies were assessed based on their methodological quality using predefined criteria. The analysis revealed a moderate trend towards reduced TB incidence rates in areas with active surveillance compared to control regions over the study period, though variability was noted among studies. While DiD provided consistent results across selected studies, heterogeneity in study designs and data collection methods indicates room for improvement in methodological consistency. Future research should consider harmonizing methodologies. To enhance reliability and comparability of surveillance system evaluations, researchers are encouraged to adopt standardised protocols and reporting guidelines. Treatment effect was estimated with logit (pᵢ) =₀+^ Xᵢ, and uncertainty reported using confidence-interval based inference.