The situation of the ongoing fifth epidemic (beginning October,2016) of human infection with avian influenza A (H7N9) virus are more serious than the first four ones.As of March 8,2017,the fifth epidemic reported 40.00％ of the cumulative cases.Recently,the pathogenic study reported two new human infections in Guangdong with an influenza A(H7N9)virus strain for which gene sequencing analysis revealed mutations in the haemagglutinin (HA) gene that resulted in the insertion of basic amino acids at the cleavage site of this protein,known to confer increased pathogenicity in chickens.However,most strains show no obvious difference in pathogenic characteristics compared with those detected during the first four waves.Although epidemiological studies showed that 3 clusters with limited human-to-human transmission have been investigated during the current wave,there are no indications of sustained person-to-person spread.Based on epidemic analysis and risk assessment results,it's likely that human infections with H7N9 virus will continue to occur in China,but epidemiological and pathogenic analysis suggested that it's unlikely to have a continued transmission of this virus.Profound public health significance would be presented by strengthening etiology and epidemiology studies of avian influenza A(H7N9) virus.%2016年10月起至今发生的第5波人感染H7N9禽流感疫情比前4波严重,截止至2017年3月8日,本波疫情感染者数量已达历年累积报告数的40.00％.病原学研究发现最近广东分离的两株H7N9病毒在HA的链接肽位置发生插入性变异导致对禽致病性有所增强,但绝大多数分离株与前4波疫情中H7N9病毒病原学特征无明显区别;流行病学调查研究显示,除有3起可能人传人事件外,与前4波比较,患者之间也没有明显的流行病学关联.因此,基于疫情分析及风险评估认为H7N9禽流感仍会扩散传播并继续发生新发病例,但流行病学和病原学分析认为该病毒在人际间持续传播的可能性低.本综述认为加强H7N9禽流感病原学与流行病学的研究具有重要的公共卫生意义.
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