Surveillance for circulation and genetic evolution of avian influenza A (H7N9) virus in poultry markets in Guangzhou, 2014−2017

Objective To understand the circulation and gene evolution of avian influenza A (H7N9) virus in Guangzhou and provide research data for prevention and control of human infection with avian influenza A (H7N9) virus.

Methods The samples were collected in poultry markets in Guangzhou during 2014–2017. Avian influenza A (H7N9) virus was detected by real-time RT-PCR, and the HA gene was plotted for phylogenetic tree.

Results A total of 28 252 samples were detected, in which 888 were positive for H7N9 virus (3.14%). The circulation peak of H7N9 virus occurred during February–May. The highest detection rate was 13% in April. The nucleotide homology of HA gene was 88.6%–100%, and the amino acid homology was 92.0%–100%. The highly pathogenic avian influenza A (H7N9) virus has been detected in the environment in 2017. Evolutionary analysis revealed that the HA gene exhibited multiple evolutionary branching characteristics. In recent years, the virus HA gene has been localized, belonging to the Southern China branch. And we have detected the isolate belonging to other evolution branch from wild birds.

Conclusion Avian influenza A (H7N9) virus continued to exist in Guangzhou during 2014–2017, and the virus mutated rapidly. It is necessary to strengthen the surveillance for avian influenza A (H7N9) virus in wild birds.