Influenza A/H9 viruses circulate worldwide in wild and domestic avian species, continuing to evolve and posing a zoonotic risk. A substantial increase in human infections with A/H9N2 subtype avian influenza viruses (AIVs) and the emergence of novel reassortants carrying A/H9N2-origin internal genes has occurred in recent years. Different names have been used to describe the circulating and emerging A/H9 lineages. To address this issue, an international group of experts from animal and public health laboratories, endorsed by the WOAH/FAO Network of Expertise on Animal Influenza, has created a practical lineage classification and nomenclature system based on the analysis of 10,638 hemagglutinin sequences from A/H9 AIVs sampled worldwide. This system incorporates phylogenetic relationships and epidemiologic characteristics designed to trace emerging and circulating lineages and clades. To aid in lineage and clade assignment, an online tool has been created. This proposed classification enables rapid comprehension of the global spread and evolution of A/H9 AIVs.

A/H9 流感病毒在世界范围内的野生和家养鸟类中传播，并持续进化并构成人畜共患风险。近年来，人类感染 A/H9N2 亚型禽流感病毒 (AIV) 的人数大幅增加，并且出现了携带 A/H9N2 起源内部基因的新型重配病毒。不同的名称被用来描述流行的和新兴的 A/H9 谱系。为了解决这个问题，来自动物和公共卫生实验室的国际专家组在 WOAH/FAO 动物流感专业网络的支持下，基于对来自 A/A 的 10,638 个血凝素序列的分析，创建了一个实用的谱系分类和命名系统。 H9 AIV 在全球范围内进行采样。该系统结合了系统发育关系和流行病学特征，旨在追踪新兴和循环的谱系和进化枝。为了帮助谱系和进化枝分配，创建了一个在线工具。这种提议的分类能够快速理解 A/H9 AIV 的全球传播和演变。