Epidemiological characteristics of influenza in Hebei province from 2016 to 2018

Objective To analyze the epidemiological characteristics of influenza in Hebei province from 2016 to 2018, so as to provide scientific basis for prevention and control of influenza. Methods The surveillance data of influenza-like illness (ILI) cases in Hebei province from 2016 to 2018 were collected from the Chinese National Influenza Surveillance Network and were analyzed by statistical methods. Results From 2016 to 2018, the average percentage of hospital visit among ILI cases was 1.64% in the influenza sentinel hospitals. The percentage of hospital visit among ILI cases in 2017-2018 was higher than that of the previous year. A total of 38 589 nasopharyngeal swab samples from ILI patients were collected and tested, from which 5 967 specimens were positive of influenza virus nucleic acid and the positive rate was 15.46%. The detection peaks of influenza virus were in winter, and the highest positive rate was in the 5-14 year old group. The predominant pathogens varied in different years. Influenza A(H3N2) was dominant in 2016-2017 while influenza A(H1N1) pdm09 and influenza B virus were dominant in 2017-2018. The detection rate of influenza and the peak value in 2017-2018 were higher than those in 2016-2017. A total of 29 outbreaks were reported from 2016 to 2018, including 20 outbreaks in primary schools (68.97%). Conclusions The influenza epidemic peaks occurred in winter in Hebei province, and the infections were intensive in the age group of 5-14 years old. The epidemic intensity of influenza was higher in 2017-2018. The influenza epidemic occurred mainly in primary schools, and the prevention and control should be enhanced for these places. Key words: Influenza surveillance; Epidemic outbreak; Epidemiological characteristics