[Distribution and gene characteristics of H3, H4 and H6 subtypes of low pathogenic avian influenza viruses in environment related avian influenza viruses during 2014-2021 in China].

Objective: To analyze the characteristics of low pathogenic H3, H4 and H6 subtypes of avian influenza viruses in environment related avian influenza viruses in China from 2014 to 2021. Methods: Surveillance sites were located in 31 provinces, autonomous region and municipalities to collect environmental samples related to avian influenza, detect the nucleic acid detection of influenza A virus, isolate virus, deeply sequence, analyze pathogenicity related molecular sites, and determine the distribution and variation characteristics of common H3, H4 and H6 subtypes of avian influenza virus in different regions, places and sample types. Results: A total of 388 645 samples were collected. The positive rate of low pathogenic H3 (0.56‰) and H6 (0.53‰) was higher than that of H4 (0.09‰). The positive rate of H4 subtype virus in live poultry market was higher than that in other places, and the difference was statistically significant. The positive rate of H3 and H6 subtypes in sewage samples was higher than that in other samples, and the difference was statistically significant. The positive rate of H3, H4 and H6 viruses in the south was higher than that in the north, and the difference was statistically significant. December was the most active time for virus. The analysis of pathogenicity related molecular sites showed that H3, H4 and H6 subtypes of viruses combined with avian influenza virus receptors, and some gene sites related to increased pathogenicity had mutations. Conclusion: The H3, H4 and H6 subtypes of low pathogenic avian influenza viruses have a high isolation positive rate in the live poultry market and sewage. The distribution of the three subtypes of viruses has obvious regional and seasonal characteristics, and the genetic characteristics still show the feature of low pathogenic avian influenza.目的： 分析2014—2021年我国禽流感相关环境中低致病性H3、H4和H6亚型禽流感病毒的特征。 方法： 在31个省、自治区和直辖市设立监测点，开展禽流感相关环境样本的采集、甲型流感病毒核酸检测、病毒分离、深度测序和致病性相关分子位点的分析，确定其中常见的H3、H4和H6亚型禽流感病毒在不同地区、不同场所和不同样本类型中的分布及病毒变异特征。 结果： 共采集388 645份样本。低致病性H3（0.56‰）和H6亚型（0.53‰）的分离阳性率高于H4亚型（0.09‰）；H4亚型病毒在活禽市场的分离阳性率高于其他场所，差异有统计学意义；H3和H6亚型病毒在污水样本的分离阳性率高于其他样本类型，差异有统计学意义；H3、H4和H6亚型病毒南方地区分离阳性率高于北方地区，差异有统计学意义；12月份是病毒最为活跃的时间。致病性相关分子位点的分析显示，H3、H4和H6亚型病毒结合禽流感病毒受体，与致病性增强相关的某些基因位点发生了突变。 结论： 低致病性禽流感H3、H4和H6亚型病毒在活禽市场和污水中具有较高的分离阳性率，3种亚型病毒的分布具有明显的地域特征和季节性，基因特征仍表现为低致病性禽流感特点。.