Surveillance and phylogenetic characteristics of H7N9 avian influenza virus in the live poultry related external environment of Quanzhou city during 2014-2017 / 中华实验和临床病毒学杂志

ABSTRACT

Objective@#To analyze the distribution and the molecular biological characteristics of variant subtypes (H5, H7 and H9) of avian influenza virus (AIV) in the live poultry related external environment of Quanzhou form 2014 to 2017, and provide regional references for the prevention, control and early-warning of human infections.@*Methods@#Samples from monitoring sites of live poultry were collected in Quanzhou from 2014 to 2017. Influenza A and variant subtypes of AIV (H5, H7 and H9) were detected by real time RT-PCR, and the detection results were further analyzed statistically. Furthermore, the HA and NA genes of four representative H7N9 strains were sequenced, and the results were further analyzed with DNAstar and MEGA7.0.@*Results@#Among the samples from external environment, the positive rate of nucleic acid of influenza A was 29.04% (377/1 289), of which the positive rates of H5, H7 and H9 subtypes were 3.80%, 13.34% and 12.02%, respectively. The positive rate of H7N9 was higher than those of the other subtypes in all monitored years, of which the highest rate was found in 2017 (21.88%). As to the different types of samples, chopping board possessed the highest positive rate of influenza A (65.4%), followed by waste water (59.3%) and drinking water for the poultry (29.6%). Among the different monitoring sites, the positive rate of poultry farm is 6.94%, far lower than that in the open air (61.7%) and the live poultry trading market (52.8%). Sequencing of the HA and NA genes of four strains of H7N9 showed that the strains from external environment and the strains from H7N9 patients belonged to Pearl River Delta and Yangtze River Delta lineage, respectively. The cleavage sites of HA proteins of these four strains were all PKGR/G without highly pathogenic mutation. Meanwhile, they were low pathogenic H7N9 without oseltamivir resistant mutation (R292 K in NA), while they all possessed the E627 K mutation in the PB2 genes associated with virulence.@*Conclusions@#H7N9 AIV existed in the live poultry related external environment of Quanzhou, especially the farmers’ and the live poultry trading market, so that more persistent surveillance could be needed in the future.