Evolution, Molecular ; Humans ; Influenza A virus ; genetics ; Influenza, Human ; epidemiology

China ; epidemiology ; Hemagglutinin Glycoproteins, Influenza Virus ; genetics ; Humans ; Influenza B virus ; genetics ; Influenza, Human ; epidemiology ; genetics

Genes, Viral ; genetics ; Humans ; Influenza A Virus, H1N1 Subtype ; genetics ; Influenza, Human ; epidemiology ; virology ; Reassortant Viruses ; genetics

DNA Damage ; Influenza A Virus, H1N1 Subtype ; Influenza, Human/*genetics ; Mutagenesis, Insertional/*genetics

Animals ; Birds ; Hemagglutinin Glycoproteins, Influenza Virus ; genetics ; immunology ; Humans ; Influenza A virus ; genetics ; immunology ; pathogenicity ; Influenza in Birds ; immunology ; pathology ; virology ; Influenza, Human ; immunology ; pathology ; virology ; Virulence ; genetics

Twelve nucleotides located at the 3′ end of viral genomic RNA (vRNA) are conserved among influenza A viruses (IAV) and have a promoter function. Hoffmann's 8-plasmid reverse genetics vector system introduced mutations at position 4, C nucleotide (C4) to U nucleotide (U4), of the 3′ ends of neuraminidase (NA) and matrix (M) vRNAs of wild-type A/PR/8/34 (PR8). This resulted in a constellation of C4 and U4 vRNAs coding for low (polymerases) and relatively high (all others) copy number proteins, respectively. U4 has been reported to increase promoter activity in comparison to C4, but the constellation effect on the replication efficiency and pathogenicity of reverse genetics PR8 (rgPR8) has not been fully elucidated. In the present study, we generated 3 recombinant viruses with C4 in the NA and/or M vRNAs and rgPR8 by using reverse genetics and compared their pathobiological traits. The mutant viruses showed lower replication efficiency than rgPR8 due to the low transcription levels of NA and/or M genes. Furthermore, C4 in the NA and/or M vRNAs induced lower PR8 virus pathogenicity in BALB/c mice. The results suggest that the constellation of C4 and U4 among vRNAs may be one of the multigenic determinants of IAV pathogenicity.
Animals ; Clinical Coding ; Influenza A virus ; Influenza, Human* ; Mice ; Neuraminidase* ; Nucleotides ; Orthomyxoviridae* ; Reverse Genetics ; RNA* ; Virulence*

Humans ; Influenza A Virus, H5N1 Subtype ; classification ; genetics ; pathogenicity ; Influenza Vaccines ; immunology ; Influenza, Human ; drug therapy ; prevention & control ; transmission ; Vaccination

BACKGROUNDTo understand the characterization of genome of a strain of avian influenza A H9N2 virus repeatedly isolated from a child with influenza illness. Thereafter to reveal the origin of this H9N2 virus.

METHODSViruses were passed in embryonated hen eggs and virion RNA was extracted from allantoic fluid and reverse transcribed to synthesize cDNA. cDNA was amplified by PCR and the PCR product was purified with a purification kit. Afterwards RNA sequence analysis was performed by dideoxynucleotide chain termination and a cloning method. Finally, phylogenetic analysis of the sequencing data was performed with MegAlign (Version 1.03) and Editseg (Version 3.69) softwares.

RESULTSGenome of A/Guangzhou/333/99 (H9N2) virus was closely related to avian influenza A H9N2 virus, but obvious difference from that of A/Duck/Hong Kong/Y439/97(H9N2) virus, as well as its genome did not include any RNA segment derived from human influenza A virus. However, the genes encoding the HA,NA,NP and NS proteins of A/Guangzhou/333/99 virus were derived from those of G9 lineage virus, the rest genes encoding the M and three polymerase (PB2,PB1 and PA) proteins were derived from G1 lineage strain.

CONCLUSIONSA/Guangzhou/333/99 virus was a reassortant derived from reassortment betweenG9 and G1 lineages of avian influenzaA(H9N2) viruses. Therefore, the most possibility is that it is derived from avian influenza A virus directly. The results do not only demonstrate that avian influenza A (H9N2) virus could infect men, but also firstly prove that the genetic reassortment could be occurred between different genetic lineages of avian influenza A (H9N2) viruses in the nature.

Animals ; Base Sequence ; Chick Embryo ; Child ; Genome, Viral ; Humans ; Influenza A Virus, H9N2 Subtype ; Influenza A virus ; genetics ; Influenza, Human ; virology ; Phylogeny

Since the first human case of influenza A virus subtype H7N9 was reported in Shanghai, China in March 2013, there have been two H7N9-infected children and one healthy H7N9 carrier. With a brief introduction to the basic information of the three children, this paper discusses the variation of Avian influenza virus by referring to the literature, suggests that human-to-human transmission is not confirmed in the small outbreak, and reviews the measures for preventing and treating H7N9 infection in humans. In addition, this paper talks about the use of tamiflu in early stage of infection and the use of peramivir when the patient's condition is severe.
Animals ; Birds ; Child ; Child, Preschool ; Humans ; Influenza A virus ; genetics ; Influenza in Birds ; virology ; Influenza, Human ; drug therapy ; prevention & control ; transmission

From February 2013, a novel avian influenza A H7N9 virus causing human infection with fatal outcomes has been identified in eastern China. This avian influenza A H7N9 virus is a triple reassortant of viruses that are avian-origin only and it is low pathogenic in poultry. Several characteristic amino acid mutations in HA and PB2 polymerase subunit (including G186V, Q226L and E627K substitution) have been found through sequence analysis, and these mutations probably facilitate binding to human-type receptors and efficient replication in mammals. Other mutations in NA, M2 and NS genes were also found. Although sustained human-to-human transmission has not been conclusively established, limited human-to-human transmission of the H7N9 virus remains possible. Intensified surveillance for the H7N9 virus in humans and animals is needed to answer questions about the viral origin, spread and potential threat.
Animals ; Birds ; virology ; China ; epidemiology ; Humans ; Influenza A virus ; genetics ; Influenza in Birds ; virology ; Influenza, Human ; transmission ; virology ; Mutation