Evolution and Antigenic Drift of Influenza A (H7N9) Viruses, China, 2017-2019.

Jiahao Zhang,Bo Li,Zhaoping Liang,Weixin Jia,Wenbao Qi,Hejia Ye,Huanan Li,Yiqun Chen,Ming Liao,Weihong Qiu,Ziwen Qiu,Kaixiong Ma

doi:10.3201/eid2608.200244

Abstract

After a sharp decrease of influenza A(H7N9) virus in China in 2018, highly pathogenic H7N9 viruses re-emerged in 2019. These H7N9 variants exhibited a new predominant subclade and had been cocirculating at a low level in eastern and northeastern China. Several immune escape mutations and antigenic drift were observed in H7N9 variants.

Highlights

Since emerging in China in 2013, influenza A(H7N9) viruses have continued to circulate in mainland China, sporadically causing human infection (1–3)
Phylogenic analysis demonstrated that the HA and NA genes of all of these highly pathogenic avian influenza (HPAI) H7N9 viruses belonged to the Yangtze River Delta lineage and formed a new subclade (Figure 1, panel A), which exhibited a long genetic distance to the HPAI H7N9 viruses that persisted during 2017–2018
We observed that the HPAI H7N9 viruses in eastern and northeastern China belonged to sublineage B-2 (Figure 2, panel B)

Summary

Introduction

Since emerging in China in 2013, influenza A(H7N9) viruses have continued to circulate in mainland China, sporadically causing human infection (1–3). Qi); National Avian Influenza Para-Reference Laboratory, Ministry of Agriculture and Rural Affairs of the People’s Republic of China, Guangzhou Qi); Key Laboratory of Animal Vaccine Development, Ministry of Agriculture and Rural Affairs of the People’s Republic of China, Guangzhou

Results

Conclusion