Public health surveillance systems are crucial for monitoring infectious diseases in Tanzania. However, their reliability and effectiveness need rigorous evaluation. A mixed-method approach combining quantitative analysis with qualitative interviews was employed to assess system performance. The quasi-experimental design revealed that the average response time for reporting suspected cases was reduced by 15% compared to baseline data, indicating improved system efficiency. This study provides evidence of a significant improvement in public health surveillance systems' reliability in Tanzania. Further systematic evaluations and continuous training are recommended to sustain these improvements. public health surveillance, quasi-experimental design, reliability assessment, infectious diseases Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.