Estimating the incidence of the 2018–2019 influenza season in Beilun district of Ningbo city, Zhejiang

  Objective  To estimate the actual case number and incidence rate of influenza in 2018–2019 season in Beilun district of Ningbo and evaluate the actual local incidence level of influenza.

  Methods  Retrospective analysis was adopted. Based on Ningbo regional health medical big data platform and influenza surveillance network platform and through the big data mining technology, all the records of acute upper respiratory tract infections in the district were obtained, and combined with the influenza nucleic acid positive rate, the case number and incidence rate of influenza in 2018–2019 season in Beilun were estimated.

  Results  From October 2018 to September 2019, the estimated case number of influenza ranged from 27 683 to 115 123 approximately, and the estimated incidence rate of influenza ranged from 4.14% to 17.23% approximately in Beilun, significantly higher than the reported data. The incidence rate was highest in age group 0–4 years, ranging from 29.28% to 76.81%, and the incidence rate in age group 5–14 years ranged from 17.31% to 46.61%. The estimated case number of influenza was highly consistent with the incidence trend of reported cases with statistical significance (r_s1=0.914, r_s2=0.923, P<0.001).

  Conclusion  The local incidence rate of influenza was significantly higher than the reported one. Age groups <15 years and >60 years are key populations in the prevention and control of influenza. It is necessary to expand and increase the coverage of influenza vaccination in these two age groups.