Evaluation of early warning effect of varicella in Maanshan, Anhui, 2016–2021: based on three methods

  Objective  To explore appropriate early warning method of varicella epidemic in Maanshan of Anhui province, and provide evidence for the timely prevention and control of varicella epidemic.

  Methods  By using moving percentile method, cumulative sum control chart method, exponential weighting smoothing method, the surveillance data of varicella in Maanshan during 2016−2021 were analyzed, and the sensitivities, the specificities, the positive predictive values, the negative predictive values and Youden's indexes of the three methods were compared and evaluated.

  Results  The cumulative sum control chart method (h=0.5, k=1.5) had the best early warning effect with the sensitivity and specificity of 100.00% respectively. The sensitivity and specificity of moving percentile method with P95 were 100.00%, 94.59%, respectively. The sensitivity and specificity of exponential weighting smoothing method (k=1, λ=0.15) were 99.33%, 89.19%, respectively.

  Conclusion  In this study, the three early warning methods had good effects, but the moving percentile method and the cumulative sum control chart method were more suitable for the practical use at grass roots level.