The circulation of highly pathogenic avian influenza viruses (HPAIVs) of various subtypes (e.g., H5N1, H5N6, H5N8, and H7N9) in poultry remains a global concern for animal and public health. Migratory waterfowls play important roles in the transmission of these viruses across countries. To monitor virus spread by wild birds, active surveillance for avian influenza in migratory waterfowl was conducted in Mongolia from 2015 to 2019. In total, 5000 fecal samples were collected from lakesides in central Mongolia, and 167 influenza A viruses were isolated. Two H5N3, four H7N3, and two H7N7 viruses were characterized in this study. The amino acid sequence at hemagglutinin (HA) cleavage site of those isolates suggested low pathogenicity in chickens. Phylogenetic analysis revealed that all H5 and H7 viruses were closely related to recent H5 and H7 low pathogenic avian influenza viruses (LPAIVs) isolated from wild birds in Asia and Europe. Antigenicity of H7Nx was similar to those of typical non-pathogenic avian influenza viruses (AIVs). While HPAIVs or A/Anhui/1/2013 (H7N9)-related LPAIVs were not detected in migratory waterfowl in Mongolia, sporadic introductions of AIVs including H5 and H7 viruses into Mongolia through the wild bird migration were identified. Thus, continued monitoring of H5 and H7 AIVs in both domestic and wild birds is needed for the early detection of HPAIVs spread into the country.

中文翻译：

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2017年至2019年从蒙古迁徙水禽中分离出的H5和H7禽流感病毒的遗传和抗原表征。

家禽中各种亚型（例如H5N1，H5N6，H5N8和H7N9）的高致病性禽流感病毒（HPAIV）的流通仍然是动物和公共健康的全球关注问题。迁徙水禽在这些病毒跨国家传播中起着重要作用。为了监测野禽传播的病毒，2015年至2019年在蒙古进行了对迁徙水禽中禽流感的主动监测。总共从蒙古中部湖边收集了5000份粪便样本，并分离出167种甲型流感病毒。在这项研究中鉴定了两种H5N3，四种H7N3和两种H7N7病毒。这些分离物的血凝素（HA）切割位点的氨基酸序列表明鸡的致病性较低。系统发育分析表明，所有H5和H7病毒都与最近从亚洲和欧洲的野生鸟类分离出的H5和H7低致病性禽流感病毒（LPAIV）密切相关。H7Nx的抗原性与典型的非致病性禽流感病毒（AIV）相似。虽然在蒙古的迁徙水禽中未检测到HPAIV或与A / Anhui / 1/2013（H7N9）相关的LPAIV，但已鉴定出通过野禽迁移向蒙古零星地引入了包括H5和H7病毒在内的AIV。因此，需要对家禽和野禽中的H5和H7 AIV进行持续监测，以及早发现传播到该国的HPAIV。虽然在蒙古的迁徙水禽中未检测到HPAIV或与A / Anhui / 1/2013（H7N9）相关的LPAIV，但已鉴定出通过野禽迁移向蒙古零星地引入了包括H5和H7病毒在内的AIV。因此，需要对家禽和野禽中的H5和H7 AIV进行持续监测，以及早发现传播到该国的HPAIV。虽然在蒙古的迁徙水禽中未检测到HPAIV或与A / Anhui / 1/2013（H7N9）相关的LPAIV，但已鉴定出通过野禽迁移向蒙古零星地引入了包括H5和H7病毒在内的AIV。因此，需要对家禽和野禽中的H5和H7 AIV进行持续监测，以及早发现传播到该国的HPAIV。