Epidemiology and etiology of influenza in Hubei province, 2016–2019

  Objective  To understand the epidemiologic and etiologic characteristics of influenza in Hubei province from 2016 to 2019 and provide laboratory evidence for the prevention and control policy development and risk assessment of influenza in Hubei.

  Methods  Combined with the results of etiologic surveillance and epidemiologic investigation of influenza network surveillance laboratory, the epidemiological analysis of influenza surveillance data in Hubei was carried out.

  Results  The average proportion of influenza like illness (ILI) cases in Hubei during 2016–2019 was 2.90%. The ILI proportion was highest in 0–5-year-old group (61.83%), and lowest in people over 60 years old (3.69%). The average influenza virus positive rate in the annual sentinel surveillance during 2016–2019 was 14.06%. A total of 4991 strains of influenza viruses were isolated, and antigenic analysis was conducted for 565 strains. Influenza A (H1N1) pdm09 virus, seasonal influenza A (H3N2) virus and influenza B virus Victoria lineage circulated alternatively with seasons. During this period, a total of 343 outbreaks of ILI, mainly in winter and spring, were reported.

  Conclusion  The annual circulation of influenza viruses showed peak in winter and spring, and sub-peak in summer in Hubei during 2016–2019, Different type influenza viruses circulated alternatively. Influenza epidemic is prone to occur in winter and spring.