Human Infection with Influenza A(H7N9) Virus during 3 Major Epidemic Waves, China, 2013-2015

Emerg Infect Dis. 2016 Jun;22(6):964-72. doi: 10.3201/eid2206.151752.


Since March 2013, a novel influenza A(H7N9) virus has caused 3 epidemic waves of human infection in mainland China. We analyzed data from patients with laboratory-confirmed influenza A(H7N9) virus infection to estimate the risks for severe outcomes after hospitalization across the 3 waves. We found that hospitalized patients with confirmed infections in waves 2 and 3 were younger and more likely to be residing in small cities and rural areas than were patients in wave 1; they also had a higher risk for death, after adjustment for age and underlying medical conditions. Risk for death among hospitalized patients during waves 2 and 3 was lower in Jiangxi and Fujian Provinces than in eastern and southern provinces. The variation in risk for death among hospitalized case-patients in different areas across 3 epidemic waves might be associated with differences in case ascertainment, changes in clinical management, or virus genetic diversity.

Keywords: China; clinical severity; epidemiology; influenza; influenza A(H7N9); respiratory infections; viruses.

Publication types

  • Historical Article

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Child
  • Child, Preschool
  • China / epidemiology
  • Disease Outbreaks*
  • Female
  • Genotype
  • Geography, Medical
  • History, 21st Century
  • Hospitalization
  • Humans
  • Infant
  • Infant, Newborn
  • Influenza A Virus, H7N9 Subtype / classification
  • Influenza A Virus, H7N9 Subtype / genetics*
  • Influenza, Human / epidemiology*
  • Influenza, Human / history
  • Influenza, Human / transmission
  • Influenza, Human / virology*
  • Male
  • Middle Aged
  • Mortality
  • Population Surveillance
  • Young Adult