Acta Veterinaria et Zootechnica Sinica ›› 2021, Vol. 52 ›› Issue (5): 1218-1229.doi: 10.11843/j.issn.0366-6964.2021.05.008

• REVIEW • Previous Articles     Next Articles

The Epidemiology of H9N2 Avian Influenza Virus in China

SUN Huapeng, CUI Xinxin, PAN Liangqi, XU Fengxiang, LI Shuo, WU Meihua, ZHU Xuhui, YU Yanan, LI Mingliang, LIU Yang, QU Xiaoyun, LIAO Ming, SUN Hailiang*   

  1. National Local Joint Engineering Laboratory of Zoonosis Prevention and Control Agents, Guangdong Laboratory of Modern Agricultural Science and Technology in Lingnan, Guangdong Key Laboratory for Prevention and Control of Zoonotic Diseases, Guangzhou 510642, China
  • Received:2020-10-15 Online:2021-05-23 Published:2021-05-22

Abstract: Outbreaks and circulation of H9N2 avian influenza viruses (AIVs) not only cause huge economic losses to poultry industry but also pose a potential threat to public health. In order to illustrate the current epidemiology of H9N2 AIVs in China, their antigenicity, receptor-binding feature and pathogenicity were summarized and viruses that circulated in 2016-2020 were analyzed. The results showed that H9N2 AIVs circulated in more than 20 provinces or cities of China, of which outbreaks occurred more in Jiangxi, Guangdong, Guizhou and Jiangsu. H9N2 AIVs were mainly isolated from chickens, and a few were isolated form waterfowl or small poultry. H9N2 AIVs were sporadically isolated from humans. Most of H9N2 AIVs fell into the clade of h9.4.2.5, and a few isolates belonged to the clade of h9.4.2.1. Current H9N2 AIVs exhibit dual receptor-binding tropism or preferentially binding to α-2-6 SA receptors. The amino acids at the antigen-related sites are polymorphic and the antigenicity is undergoing changes. Some adaptation mutations in PB2, PA and HA protein which enhancing viruses’ replication in mammalian cells and their pathogenicity to mice, were acquired, and those increased the risk of viruses to break through species-barriers to infect other mammals including human. Taken together, the surveillance of H9N2 AIVs and monitoring their variation of antigenicity and pathogenicity should be strengthened.

Key words: H9N2 AIV, evolution, receptor, pathogenicity, antigenicity

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