An overview of the epidemiology and emergence of influenza A infection in humans over time

Abstract

In recent years multiple novel influenza A strains have emerged in humans. We reviewed publically available data to summarise epidemiological characteristics of distinct avian influenza viruses known to cause human infection and describe changes over time. Most recently identified zoonotic strains have emerged in China (H7N9, H5N6, H10N8) - these strains have occurred mostly in association with visiting a live bird market. Most zoonotic AIVs and swine influenza variants typically cause mild infections in humans however severe illness and fatalities are associated with zoonotic H5N6, H10N8, H7N9 and H5N1 serotypes, and the H1N1 1918 Spanish Influenza. The changing landscape of avian influenza globally indicates a need to reassess the risk of a pandemic influenza outbreak of zoonotic origin.

Keywords: Avian influenza; Emerging infectious diseases; Influenza A; One health.

Fig. 1

Timeline of Influenza A serotype emergence by year and zoonotic host from 1918 to 2015. Each point indicates a distinct avian influenza serotype known to have caused human infection, placement of point corresponds to their year of emergence. The different point shapes correspond to the animal host which was identified when the serotype was first reported in humans: a pentagon corresponds to a seal host, a triangle corresponds to avian host, a cross corresponds to swine host, and a circle corresponds to instances where the animal host has not yet been identified