Application of moving epidemic method to study influenza epidemic intensity in winter and spring in Ningbo

ObjectiveTo use moving epidemic method (MEM) to study the epidemic intensity of seasonal influenza epidemic in Ningbo, establish influenza surveillance and early warning mechanism and provide evidence for the prevention and control of influenza.

MethodsThe positive rates of virus detection in winter and spring influenza season in Ningbo from 2013 to 2018 (40^th week to the 20^th week next year) were used, the MEM model was established to analyze the epidemic intensity of the seasonal influenza epidemic in Ningbo from 2018 to 2019.

ResultsIn the period of 2018–2019, the threshold of the initial influenza epidemic period in Ningbo was 22.68%, and the threshold of the late epidemic period was 23.32%. The initial epidemic period was from the 40^th week of 2018 to the 1^st week of 2019. In the 2^nd week of 2019, the influenza incidence broke through the initial threshold and the epidemic intensity was low, and a medium epidemic intensity was recorded from the 3^rd week. From the 8^th week to the 9^th week, the influenza epidemic intensity was high. The epidemic intensity gradually decreased to medium level from the 10^th week to the 14^th week and reached a low epidemic level from the 14^th week to the 18^th week. After the 19^th week, it was the late epidemic period. The sensitivity of the MEM model was 80.04%, the specificity of the MEM model was 87.18%. The goodness of the model was good.

ConclusionThe start time and intensity of influenza epidemic can be calculated by using the influenza early warning model established with MEM, and the model can be directly evaluated. This method provides a scientific basis for the early identification and early warning of influenza epidemic.