Epidemiological analysis of influenza surveillance in Changzhou from 2010 to 2016

Objective To study the epidemiological characteristics of influenza in Changzhou during 2010-2016, and to provide references for developing strategies regarding the prevention and control of influenza. Methods Data concerning influenza like illness (ILI) and etiological detection were collected from the national influenza network surveillance system. Descriptive epidemiology was employed to analyze the epidemiological and etiological features of ILI in Changzhou during 2010-2016. Results There were altogether 97 400 ILI cases that were reported from 2010 to 2016 in Changzhou, with the average annual consultation rate of influenza like illness (ILI%) being 1.85%. The ILI% was significantly different among different years (χ²=16 461.59,P<0.001). The ILI% showed two peak seasons which distributed in winter-spring and summer. Instances with patients between 5 and 14 years old and patients under 5 years old were the most numerous in the sphere of ILI cases. Positive rate of pathogen detection was significantly different among different years (χ²=230.34,P<0.001). Type B and type A (H3) were the main types of flu strains and occasionally an epidemic of type A (H1N1) was present. Positive rate of etiological detection was positively correlated with ILI% (r_s=0.26,P=0.017). Conclusions The epidemic flu strains in winter-spring were type B and type A (H1N1), whereas the epidemic flu strain in summer switched to type A (H3). Vaccination is an important means to protect high-risk groups which are under 15 years old from influenza virus.