Abstract
The aim of the present study was to analyze the evolution and variation of a novel strain of the avian influenza virus. The virus-positive specimens [A/Changsha/2/2013 (H7N9)] from a patient infected with the novel avian influenza A (H7N9) virus was amplified by reverse transcription-PCR and the full genome was sequenced. The sequencing results were submitted to GenBank and then analyzed by phylogenetic tree analysis using BioEdit and Mega5 software. The phylogenetic tree of the hemagglutinin (HA) and neuraminidase genes revealed that A/Changsha/2/2013 (H7N9) and all the new H7N9 viruses in 2013 were in a large cluster, and their nucleotide evolutionary distances were closely associated. Phylogenetic tree analyses of the nucleoprotein and nonstructural genes demonstrated two main branches. One branch contained novel H7N9 viruses isolated from avian, human and environmental sources in different regions. The other branch contained three novel H7N9 virus strains isolated from environmental sources in Shanghai. All the phylogenetic trees of the matrix protein, polymerase acidic, polymerase basic protein 1 and polymerase basic protein 2 genes also showed two branches, with each branch including the novel H7N9 virus strains isolated from avian, human and environmental sources in different regions. Molecular characterization demonstrated that 52 novel H7N9 viruses sequenced to date contain the G228S and G186V mutations in the receptor binding site of the HA protein. The full-genome sequences of A/Changsha/2/2013 and analyses of its molecular characteristics suggest that the A/Changsha/2/2013 H7N9 virus strain has molecular characteristics that may facilitate adaptation of the virus to mammalian hosts and may even bind to human receptors.
Highlights
The avian influenza virus is a member of the Orthomyxoviridae family of the Influenzavirus A genus
The results indicate that the new human H7N9 viruses were highly homologous to avian and environmental H7N9 viruses
More H7N9 viruses were isolated in different birds and environments, suggesting that H7N9 viruses have been distributed in these avian species and environments
Summary
The avian influenza virus is a member of the Orthomyxoviridae family of the Influenzavirus A genus. The subtypes capable of infecting humans are H5N1, H7N2, H7N3, H7N7 and H9N2. The majority of avian influenza viruses lead to mild symptoms in infected humans, which mainly include conjunctivitis or upper respiratory tract infection, with the exception of H5N1 infections, which have a mortality rate >50% [1]. A new reassortant viral subtype named H7N9 was initially isolated from a patient with a severe lower respiratory tract infection [2]. Internal genes of this virus originate from the H9N2 avian influenza virus [2]. Patients who are infected with the H7N9 virus usually present flu‐like symptoms possibly accompanied by a headache, muscle aches and general malaise. The symptoms may progress rapidly to acute respiratory distress syndrome and even lead to mortality [3]
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