ABSTRACT
Objective To analyze host adaptability and drug resistance variation of highly pathogenic avian influenza (HPAI) A(H5N6) viruses obtained from outbreaks in Suzhou City. Methods Real-time fluorescent quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay was used for influenza virus detection in pharynx or anus swabs of dead birds and suspected cases. Full genome of H5N6 positive samples were sequenced by using Sanger method. Hemagglutinin (HA) and neuramidinase (NA) phylogenetic trees were constructed by MEGA software. Results A child was laboratory confirmed to have A(H5N6) viruses infection in November 2018. A outbreak of avian flu in poultry in W district during the Spring Festival was laboratory confirmed as a A(H5N6) epidemic situation. Avian-origin H5N6 viruses possessed D198N and Q226H resistance mutations. The homology of HA and NA genes of Suzhou strains were 98.01%-100.0% and 98.16%-100.0%, respectively. These H5N6 strains belonged to 2.3.4.4 H5 clad. Multiple basic amino acid at the cleavage site of HA implied the highly pathogenic characteristics of Suzhou H5N6 strains. Conclusion H5N6 is a kind of malti-sourse reassortment virus, which is still evolving. Multiple loci of Suzhou H5N6 strains of this epidemic were identified to have drifted. The prevalence of drug-resistant mutations should be closely monitored in order to timely take effective measures to prevent serious damage to public health and poultry production industries.