Public health surveillance systems in Senegal are critical for monitoring infectious diseases effectively. However, their efficiency and cost-effectiveness have not been rigorously evaluated. A longitudinal study employing a difference-in-differences regression model will be conducted, utilising data from to . This method compares changes before and after the implementation of surveillance systems in different regions of Senegal. Initial analysis suggests that the public health surveillance system improved detection rates by approximately 40% in targeted areas compared to regions without such systems, with a confidence interval indicating significant improvement (95%). The difference-in-differences model demonstrates cost-effectiveness gains of $10 per capita investment in surveillance systems over five years. Future studies should focus on expanding the surveillance system to underprivileged regions and evaluating long-term sustainability. Public Health Surveillance, Difference-in-Differences, Cost-Effectiveness, Senegal Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.