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Diversity of Influenza Viruses in Swine and the Emergence of a Novel Human Pandemic Influenza A (H1N1)

Division of Virology, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
Influenza and Other Respiratory Viruses (Impact Factor: 1.9). 09/2009; 3(5):207-13. DOI: 10.1111/j.1750-2659.2009.00096.x
Source: PubMed

ABSTRACT The novel H1N1 influenza virus that emerged in humans in Mexico in early 2009 and transmitted efficiently in the human population with global spread has been declared a pandemic strain. Here we review influenza infections in swine since 1918 and the introduction of different avian and human influenza virus genes into swine influenza viruses of North America and Eurasia. These introductions often result in viruses of increased fitness for pigs that occasionally transmit to humans. The novel virus affecting humans is derived from a North American swine influenza virus that has acquired two gene segments [Neuraminidase (NA) and Matrix (M)] from the European swine lineages. This reassortant appears to have increased fitness in humans. The potential for increased virulence in humans and of further reassortment between the novel H1N1 influenza virus and oseltamivir resistant seasonal H1N1 or with highly pathogenic H5N1 influenza stresses the need for urgent pandemic planning.

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    • "Genetic analysis confirmed that it was a triple reassorted virus from human, swine, and avian lineages. The virus carried the HA, NP, and NS genes of classical swine virus origin, the PB2 and PA genes from North American avian viruses, the PB1 gene from viruses of human origin and the NA and M genes from Eurasian swine avian-like viruses [Brockwell-Staats et al., 2009; Garten et al., 2009; Peiris et al., 2009]. Molecular analysis of A(H1N1)pdm09 strains had classified them into seven discrete genetic clades [Nelson et al., 2009] which were also confirmed by several "
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    ABSTRACT: The pandemic H1N1 strain of Influenza A virus [A(H1N1)pdm09] is now well adapted in human populations. However, it is still causing sporadic outbreaks worldwide with different severity. The present study was planned to understand the genetic diversity (based on the HA1 gene) of influenza A(H1N1)pdm09 strains circulating during the post pandemic period. The HA1 gene was selected because the HA1 protein is immunogenic, functions as a receptor binding site and indirectly affects transmission and pathogenicity of virus. A total of 2,818 cases were enrolled. Nasal/throat swabs from all cases were tested by one-step real time PCR for detection of influenza virus types and subtypes according to the CDC protocol. Of these, 134 cases were A(H1N1)pdm09 positive, 34 of which were screened for HA1 gene (position 434–905) sequencing (Big-Dye terminator using 3130 ABI, Genetic analyzer). Molecular and phylogenetic analysis was performed using PhyML approach (v. 3.0). All A(H1N1)pdm09 positive and negative cases were clinically characterized. Phylogentically, all Lucknow strains (n = 33) except one fall with the clade seven reference strain. One strain showed 99.9% similarities with clade one reference strain A/California/07/2009. In mutational analysis, 33 strains had the S220T mutation, which is at an antigenic site and characteristic of clade seven along with few minor mutations; K180I/T/Q, V190I, S200P, S202T, A203T, A214T, S220T, V251I, and A273T. These results suggest that clade seven was the most widely circulating clade in Lucknow and A(H1N1)pdm09 cases showed mild clinical symptoms as compared to A(H3N2) or influenza B cases. J. Med. Virol. © 2014 Wiley Periodicals, Inc.
    Journal of Medical Virology 04/2014; DOI:10.1002/jmv.23946 · 2.22 Impact Factor
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    • "This virus retained gene constellation of avian (PB2 and PA), human (PB1, HA, and NA), and CS lineages (NP, M, and NS) [11]. Since then, the triple-reassortant virus has gone through multiple reassortment events and thus it diverged into various evolution routes of IAVs [12]. During these reassortment events, the triple-reassortant internal genes (TRIG) have been a gene cassette for accepting different HA and/or NA genes from other contemporary human and swine IAVs [13]. "
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    PLoS ONE 02/2014; 9(2):e88782. DOI:10.1371/journal.pone.0088782 · 3.23 Impact Factor
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    • "Influenza A viruses have been isolated from a number of animals including humans, birds, dogs, seals, horses and swine [1]. The causative agent is RNA virus with a segmented genome comprised of eight negative-sense, single-stranded RNA segments encoding eleven proteins [2]. "
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    Virology Journal 03/2011; 8(1):129. DOI:10.1186/1743-422X-8-129 · 2.09 Impact Factor
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