Evolution of the H9N2 influenza genotype that facilitated the genesis of the novel H7N9 virus

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 2; pp. 548 - 553
• Main Authors: Pu, Juan, Wang, Shuoguo, Yin, Yanbo, Zhang, Guozhong, Carter, Robert A., Wang, Jinliang, Xu, Guanlong, Sun, Honglei, Wang, Min, Wen, Chu, Wei, Yandi, Wang, Dongdong, Zhu, Baoli, Lemmon, Gordon, Jiao, Yuannian, Duan, Susu, Wang, Qian, Du, Qian, Sun, Meng, Bao, Jinnan, Sun, Yipeng, Zhao, Jixun, Zhang, Hui, Wu, Gang, Liu, Jinhua, Webster, Robert G.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 13.01.2015; National Acad Sciences
• Subjects: Adaptability; Animals; Antigenic Variation - genetics; Antigens, Viral - genetics; avian influenza; Biological Sciences; Chickens; Chickens - virology; China; China - epidemiology; Evolution; Evolution, Molecular; farms; genes; Genes, Viral; Genetic Drift; Genotype; Genotype & phenotype; Genotypes; Hemagglutinin Glycoproteins, Influenza Virus - genetics; Hemagglutinin Glycoproteins, Influenza Virus - immunology; human diseases; Humans; Influenza; Influenza A virus; Influenza A Virus, H7N9 Subtype - genetics; Influenza A Virus, H7N9 Subtype - immunology; Influenza A Virus, H7N9 Subtype - pathogenicity; Influenza A Virus, H9N2 Subtype - genetics; Influenza A Virus, H9N2 Subtype - immunology; Influenza A Virus, H9N2 Subtype - pathogenicity; Influenza in Birds - epidemiology; Influenza in Birds - virology; Influenza virus; Influenza, Human - epidemiology; Influenza, Human - virology; pandemic; Pandemics; Phylogeny; Poultry; Reassortant Viruses - genetics; Reassortant Viruses - immunology; Reassortant Viruses - pathogenicity; Retrospective Studies; viruses; China; China, People's Rep; H7N9; H9N2; infectivity; chicken influenza virus; genotype
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1422456112

The emergence of human infection with a novel H7N9 influenza virus in China raises a pandemic concern. Chicken H9N2 viruses provided all six of the novel reassortant’s internal genes. However, it is not fully understood how the prevalence and evolution of these H9N2 chicken viruses facilitated the genesis of the novel H7N9 viruses. Here we show that over more than 10 y of cocirculation of multiple H9N2 genotypes, a genotype (G57) emerged that had changed antigenicity and improved adaptability in chickens. It became predominant in vaccinated farm chickens in China, caused widespread outbreaks in 2010–2013 before the H7N9 viruses emerged in humans, and finally provided all of their internal genes to the novel H7N9 viruses. The prevalence and variation of H9N2 influenza virus in farmed poultry could provide an important early warning of the emergence of novel reassortants with pandemic potential.