Objective To examine prevalence characteristics and variation trend of influenza in Liaoning province between surveillance years of 2014 and 2017 and to provide references to influenza prevention and control.
Methods We collected data on incidence and outbreak of influenza-like illness (ILI) cases reported in Liaoning province from 14th week of 2014 to 13th week of 2017 from China Influenza Surveillance Information System and conducted statistical analyses.
Results The reported ILI cases accounted totally for 3.58% of all outpatient clinic visits (573 768 out of 16 034 584) during the period, with the yearly proportion of 3.39%, 3.33% and 3.48%. The reported ILI cases were mainly the people (n = 490 206) under the age of 15 years, accounting for 85.44% of all ILI cases, of which 59.68% were small children aged 0 – 4 years. During the 3-year period, the yearly positive rate of influenza virus isolation were 6.86%, 6.85%, and 6.28%, with the dominant strain of H3N2, By, Bv, and HIN1, respectively. There were 7, 3 and 4 outbreaks reported in each year of the period. The reported influenza outbreaks occurred mainly in winter (12 outbreaks) and in primary and secondary schools (11 outbreaks).
Conclusion The influenza epidemics were prevalent in a single annual peak pattern in winter and spring in Liaoning province between surveillance years of 2014 and 2017, with multiple and alternated dominant virus strains. The results suggest that timely surveillance on school outbreak and on the variation of antigenicity and genetic characteristics of the virus should be enhanced.
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