Molecular Evolution, Diversity, and Adaptation of Influenza A(H7N9) Viruses in China

Emerg Infect Dis. 2018 Oct;24(10):1795-1805. doi: 10.3201/eid2410.171063.

Abstract

The substantial increase in prevalence and emergence of antigenically divergent or highly pathogenic influenza A(H7N9) viruses during 2016-17 raises concerns about the epizootic potential of these viruses. We investigated the evolution and adaptation of H7N9 viruses by analyzing available data and newly generated virus sequences isolated in Guangdong Province, China, during 2015-2017. Phylogenetic analyses showed that circulating H7N9 viruses belong to distinct lineages with differing spatial distributions. Hemagglutination inhibition assays performed on serum samples from patients infected with these viruses identified 3 antigenic clusters for 16 strains of different virus lineages. We used ancestral sequence reconstruction to identify parallel amino acid changes on multiple separate lineages. We inferred that mutations in hemagglutinin occur primarily at sites involved in receptor recognition or antigenicity. Our results indicate that highly pathogenic strains likely emerged from viruses circulating in eastern Guangdong Province during March 2016 and are associated with a high rate of adaptive molecular evolution.

Keywords: China; H7N9; adaptation; avian influenza; avian influenza virus; diversity; hemagglutination inhibition assay; influenza; molecular epidemiology; molecular evolution; phylogenetics; respiratory infections; virus subtypes; viruses.

Publication types

  • Historical Article
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antigenic Variation
  • Birds
  • China / epidemiology
  • Evolution, Molecular*
  • Genetic Variation*
  • Genome, Viral
  • Genotype
  • Geography, Medical
  • History, 21st Century
  • Humans
  • Influenza A Virus, H7N9 Subtype / classification*
  • Influenza A Virus, H7N9 Subtype / genetics*
  • Influenza A Virus, H7N9 Subtype / immunology
  • Influenza A Virus, H7N9 Subtype / isolation & purification
  • Influenza in Birds / epidemiology*
  • Influenza in Birds / history
  • Influenza in Birds / virology*
  • Influenza, Human / epidemiology*
  • Influenza, Human / history
  • Influenza, Human / virology*
  • Phylogeny
  • RNA, Viral

Substances

  • RNA, Viral