Objectives
Based on the global spread of highly pathogenic avian influenza A(H5) clade 2.3.4.4b viruses, this study analyzed the epidemic and phylogenetic evolution characteristics of clade 2.3.4.4b viruses in China.
Methods
The HA gene sequences of H5 subtype clade 2.3.4.4b viruses from Global Initiative of Sharing All Influenza Database were collected and sorted out. Combined with metadata such as host source, sampling time and geographical distribution of the viruses, a phylogenetic tree was constructed based on the maximum likelihood method, and the transmission path was inferred by phylogenetic geography method to analyze the host source, temporal and spatial transmission and genetic evolution characteristics of H5 subtype clade 2.3.4.4b viruses in China from 2010 to 2023.
Results
H5N1, H5N6 and H5N8 subtypes are co-prevalent in wild waterfowl and poultry in China, and the host sources of different subtypes are different. The H5N1 and H5N8 subtypes are mainly derived from wild waterfowl, and the H5N6 subtype is mainly derived from poultry. Genetic evolutionary analysis showed that clade 2.3.4.4b viruses formed three obvious clusters according to the evolutionary time, including cluster I, II and III, which were consistent with the epidemic trend of the three global epidemics. Phylogeographic methods show that Central China is the driving center for the transmission and evolution of H5 subtype clade 2.3.4.4b viruses in China.
Conclusion
Influenza A(H5) clade 2.3.4.4b viruses continue to prevail in China, and there is an import high risk through wild bird migration and poultry trade. All-round surveillance and early warning of influenza among people, poultry and wild waterfowl should be continued to carry out. This study provides a basis for risk assessment of H5 subtype avian influenza virus in China.