Public health surveillance systems in Nigeria are essential for monitoring infectious diseases and ensuring timely interventions. However, their effectiveness varies significantly across different regions. A quasi-experimental assessment was conducted to evaluate the performance and efficiency of public health surveillance systems. The study utilised mixed-methods approaches including surveys, interviews, and data analysis. The findings suggest that there is an uneven distribution of resources across regions, with some areas experiencing higher costs for lower returns in terms of disease detection and control. The quasi-experimental design provided insights into the cost-efficiency of public health surveillance systems but also highlighted gaps in resource allocation. Recommendations include targeted investments in under-resourced regions to improve disease detection and response capabilities, thereby enhancing overall system performance. Public Health Surveillance, Nigeria, Quasi-Experimental Design, Cost-Efficiency Measurement Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.