Abstract: Abstract：Since the appearance of H7N9 avian influenza virus in China, it has caused five waves of epidemics. A highly pathogenic H7N9 mutant strain has appeared in the 5th wave of the epidemics. The insertion mutation of the HA linked peptide position of the virus strain resulted in the virulence enhancement of the virus to poultry. At the same time, the virus was isolated from human H7N9 avian influenza cases. Therefore, the etiology and epidemiology of highly pathogenic H7N9 avian influenza virus are of great significance for the prevention and control of the disease. This article reviews the mutation sources, epidemiological characteristics and control measures of highly pathogenic H7N9 avian influenza virus, and provides scientific strategies for the effective prevention and control of highly pathogenic H7N9 avian influenza.

Key words: influenza in birds, influenza A virus, H7N9 subtype, epidemiology, etiology