Objective To analyze epidemiological characteristics of influenza breaks in mainland China during 2016 – 2017 surveillance season, and to provide references for developing influenza prevention and control strategies.
Methods We collected the data on reported influenza epidemics in 2016 – 2017 surveillance season from China Influenza Surveillance Information System and China Public Health Emergency Management Information System and analyzed the data using descriptive epidemiological methods.
Results During the surveillance season, a total of 643 influenza outbreaks (with 10 or more incidences in an epidemic) in mainland China were reported, involving 17 657 patients and 2 deaths and with a mortality rate of 0.11‰. The reported influenza outbreaks occurred most frequently during December 2016 in both the southern and northern regions and an obvious increase of the outbreak was observed in March 2017 in the southern region. During the period more influenza outbreaks (556 involving 15 849 cases) were reported in the southern region than that (87involving 1 808 cases) in the north region. The highest number of the outbreaks were reported in Jiangsu province (122, 19.0% of all the outbreaks reported), followed by that in Guangxi Zhuang Autonomous Region (89, 13.8%) and Anhui province (74, 11.5%). The most (612, 95.2%) of the outbreaks occurred in primary, secondary schools and child care institutions and the majority (521, 81.0%) of the outbreaks involved 10 – 29 incident cases. The dominant isolated virus strains for the outbreaks were influenza A (H3N2) (327 50.9% of all the outbreaks,) and influenza B (181, 28.1%).
Conclusion Seasonality of influenza outbreaks was observed in mainland China during 2016 – 2017 surveillance season and the reported influenza outbreaks were most frequently occurred in winter-spring season and in southern China.
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