R G Webster

United Arab Emirates University, Al ‘Ayn, Abu Zaby, United Arab Emirates

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Publications (634)3338.59 Total impact

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    ABSTRACT: Continuous circulation of influenza A(H5N1) virus among poultry in Egypt has created an epicenter in which the viruses evolve into newer subclades and continue to cause disease in humans. To detect influenza viruses in Egypt, since 2009 we have actively surveyed various regions and poultry production sectors. From August 2010 through January 2013, >11,000 swab samples were collected; 10% were positive by matrix gene reverse transcription PCR. During this period, subtype H9N2 viruses emerged, cocirculated with subtype H5N1 viruses, and frequently co-infected the same avian host. Genetic and antigenic analyses of viruses revealed that influenza A(H5N1) clade 2.2.1 viruses are dominant and that all subtype H9N2 viruses are G1-like. Cocirculation of different subtypes poses concern for potential reassortment. Avian influenza continues to threaten public and animal health in Egypt, and continuous surveillance for avian influenza virus is needed.
    Emerging Infectious Diseases 04/2014; 20(4):542-51. · 6.79 Impact Factor
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    ABSTRACT: Avian-origin influenza A(H7N9) recently emerged in China, causing severe human disease. Several subtype H7N9 isolates contain influenza genes previously identified in viruses from finch-like birds. Because wild and domestic songbirds interact with humans and poultry, we investigated the susceptibility and transmissibility of subtype H7N9 in these species. Finches, sparrows, and parakeets supported replication of a human subtype H7N9 isolate, shed high titers through the oropharyngeal route, and showed few disease signs. Virus was shed into water troughs, and several contact animals seroconverted, although they shed little virus. Our study demonstrates that a human isolate can replicate in and be shed by such songbirds and parakeets into their environment. This finding has implications for these birds' potential as intermediate hosts with the ability to facilitate transmission and dissemination of A(H7N9) virus.
    Emerging Infectious Diseases 03/2014; 20(3). · 6.79 Impact Factor
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    ABSTRACT: Avian influenza viruses may cause severe disease in a variety of domestic animal species worldwide, with high mortality in chickens and turkeys. To reduce the information gap about prevalence of these viruses in animals in Uganda, this study was undertaken. Influenza A virus prevalence by RT-PCR was 1.1% (45/4,052) while seroprevalence by ELISA was 0.8% (24/2,970). Virus prevalence was highest in domestic ducks (2.7%, 17/629) and turkeys (2.6%, 2/76), followed by free-living waterfowl (1.3%, 12/929) and swine (1.4%, 7/511). A lower proportion of chicken samples (0.4%, 7/1,865) tested positive. No influenza A virus was isolated. A seasonal prevalence of these viruses in waterfowl was 0.7% (4/561) for the dry and 2.2% (8/368) for the wet season. In poultry, prevalence was 0.2% (2/863) for the dry and 1.4% (24/1,713) for the wet season, while that of swine was 0.0% (0/159) and 2.0% (7/352) in the two seasons, respectively. Of the 45 RT-PCR positive samples, 13 (28.9%) of them were H5 but none was H7. The 19 swine sera positive for influenza antibodies by ELISA were positive for H1 antibodies by HAI assay, but the subtype(s) of ELISA positive poultry sera could not be determined. Antibodies in the poultry sera could have been those against subtypes not included in the HAI test panel. The study has demonstrated occurrence of influenza A viruses in animals in Uganda. The results suggest that increase in volumes of migratory waterfowl in the country could be associated with increased prevalence of these viruses in free-living waterfowl and poultry.
    BMC Veterinary Research 02/2014; 10(1):50. · 1.86 Impact Factor
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    ABSTRACT: Influenza B viruses cause annual outbreaks of respiratory illness in humans and are increasingly recognized as a major cause of influenza-associated pediatric mortality. Neuraminidase (NA) inhibitors (NAIs) are the only available therapy for patients infected with influenza B viruses and the potential emergence of NAI-resistant viruses is a public health concern. The NA substitutions located within enzyme active site could not only reduce NAI susceptibility of influenza B virus but also affect virus fitness. In this study we investigated the effect of single NA substitutions on fitness of influenza B/Yamanashi/166/1998 viruses (Yamagata lineage). We generated recombinant viruses containing either WT NA or NA with a substitution in the catalytic (R371K) or framework residues (E119A, D198E, D198Y, I222T, H274Y, N294S). We assessed NAI susceptibility, NA biochemical properties, NA protein expression, and virus replication in vitro and in differentiated normal human bronchial epithelial (NHBE) cells. Our results showed that four NA substitutions (D198E, I222T, H274Y, and N294S) conferred reduced inhibition by oseltamivir and 3 (E119A, D198Y, and R371K) conferred highly reduced inhibition by oseltamivir, zanamivir, and peramivir. All NA substitutions, except for D198Y and R371K, were genetically stable after 7 passages in MDCK cells. Cell surface NA protein expression was significantly increased by H274Y and N294S substitutions. Viruses with E119A, I222T, H274Y, or N294S substitutions were not attenuated in replication efficiency in vitro or in NHBE cells. Overall, viruses with E119A or H274Y NA substitutions possess fitness comparable to NAI-susceptible virus and their acquisition by influenza B viruses should be closely monitored.
    Antimicrobial Agents and Chemotherapy 02/2014; · 4.57 Impact Factor
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    ABSTRACT: Toll-like receptors (TLRs) play key roles in innate immune recognition of pathogen-associated molecular patterns of invading microbes. Among the 10 TLR family members identified in humans, TLR10 remains an orphan receptor without known agonist or function. TLR10 is a pseudogene in mice and mouse models are noninformative in this regard. Using influenza virus infection in primary human peripheral blood monocyte-derived macrophages and a human monocytic cell line, we now provide previously unidentified evidence that TLR10 plays a role in innate immune responses following viral infection. Influenza virus infection increased TLR10 expression and TLR10 contributed to innate immune sensing of viral infection leading to cytokine induction, including proinflammatory cytokines and interferons. TLR10 induction is more pronounced following infection with highly pathogenic avian influenza H5N1 virus compared with a low pathogenic H1N1 virus. Induction of TLR10 by virus infection requires active virus replication and de novo protein synthesis. Culture supernatants of virus-infected cells modestly up-regulate TLR10 expression in nonvirus-infected cells. Signaling via TLR10 was activated by the functional RNA-protein complex of influenza virus leading to robust induction of cytokine expression. Taken together, our findings identify TLR10 as an important innate immune sensor of viral infection and its role in innate immune defense and immunopathology following viral and bacterial pathogens deserves attention.
    Proceedings of the National Academy of Sciences 02/2014; · 9.74 Impact Factor
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    ABSTRACT: Wild birds are an important but to some extent under-studied reservoir for emerging pathogens. We used unbiased sequencing methods for virus discovery in shorebird samples from the Delaware Bay, USA; an important feeding ground for thousands of migratory birds. Analysis of shorebird fecal samples indicated the presence of a novel astrovirus and coronavirus. A sanderling sample yielded sequences with distant homology to avian nephritis virus 1, an astrovirus associated with acute nephritis in poultry. A ruddy turnstone sample yielded sequences with homology to deltacoronaviruses. Our findings highlight shorebirds as a virus reservoir and the need to closely monitor wild bird populations for the emergence of novel virus variants.
    PLoS ONE 01/2014; 9(4):e93395. · 3.73 Impact Factor
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    ABSTRACT: The divergence of the hemagglutinin gene of A/goose/Guangdong/1/1996-lineage H5N1 viruses during 2011 and 2012 (807 new sequences collected through December 31, 2012) was analyzed by phylogenetic and p-distance methods to define new clades using the pre-established nomenclature system. Eight new clade designations were recommended based on division of clade 1.1 (Mekong River Delta), (Indonesia), 2.2.2 (India/Bangladesh), (Egypt/Israel), and (Asia). A simplification to the previously defined criteria, which adds a letter rather than number to the right-most digit of fifth-order clades, was proposed to facilitate this and future updates.
    Influenza Other Respir Viruses. 01/2014;
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    ABSTRACT: H6 subtype influenza viruses are commonly isolated from wild aquatic birds. However, limited information is available regarding H6 influenza virus isolated from chickens. We compared the viral genome segment between A/chicken/Hong Kong/W312/97 (H6N1), which was able to grow in chicken trachea, and A/duck/Shantou/5540/01 (H6N2), which was isolated from wild aquatic duck, to explore the factors for effective replication in chicken. When chickens were inoculated with 7 + 1 reassortants (W312 background), the replication of viruses with PB2 and M genes derived from the duck strain was significantly reduced. Chimeras of PB2 and M proteins, encoding the C-terminal region of the PB2 protein and the M2 protein from W312, were required for efficient replication in canine-derived (MDCK) cells and in chicken trachea. These results indicate that host range may be determined by some types of internal proteins such as PB2 and M2, as well as by surface glycoprotein like hemagglutinin.
    Influenza research and treatment. 01/2014; 2014:547839.
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    ABSTRACT: H2N2 influenza A viruses were the cause of the 1957-1958 pandemic. Historical evidence demonstrates they arose from avian virus ancestors, and while the H2N2 subtype has disappeared from humans, it persists in wild and domestic birds. Re-emergence of H2N2 in humans is a significant threat due to the absence of humoral immunity in individuals under the age of 50. Thus, examination of these viruses, particularly those from the avian reservoir, must be addressed through surveillance, characterization, and antiviral testing. The data presented here are a risk assessment of 22 avian H2N2 viruses isolated from wild and domestic birds over 6 decades. Our data showed that they have a low rate of genetic and antigenic evolution and remained similar to isolates circulating near the time of the pandemic. Most isolates replicated in mice and human bronchial epithelial cells, but replication in swine tissues was low or absent. Multiple isolates replicated in ferrets, and 3 viruses were transmitted to direct-contact cagemates. Markers of mammalian adaptation in HA and PB2 proteins were absent from all isolates, and they retained a preference for avian-like α2-3 linked sialic acid receptors. Most isolates remained antigenically similar to pandemic A/Singapore/1/57 (H2N2) virus, suggesting they could be controlled by the pandemic vaccine candidate. All viruses were susceptible to neuraminidase inhibitors and adamantanes. Nonetheless, the sustained pathogenicity of avian H2N2 viruses in multiple mammalian models elevates their risk potential for human infections and stresses the need for continual surveillance as a component of pre-pandemic planning.
    Journal of Virology 11/2013; · 5.08 Impact Factor
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    ABSTRACT: nfluenza A (H9N2) viruses are a genetically diverse population that infects wild and domestic avian species and mammals and contributed the internal gene segments to the A/H5N1 and A/H7N9 viruses associated with lethal human infections. Here we comprehensively assess the potential risk to mammals of a diverse panel of A/H9N2 viruses, representing the major H9N2 clades, using a combination of in vitro assays (e.g., antiviral susceptibility and virus growth in primary differentiated human airway cells) and in vivo assays (e.g., replication, transmission and/or pathogenicity of viruses in ducks, pigs, mice and ferrets). We observed that viruses isolated from humans, A/Hong Kong/1073/1999 and A/Hong Kong/33982/2009, had the highest risk potential. However, the A/swine/ Hong Kong/9A-1/1998 and A/chicken/Hong Kong/G9/1997 viruses also displayed several features suggesting a fitness profile adapted to human infection and transmission. The North American avian H9N2 clade virus had the lowest risk profile, and the other viruses tested displayed various levels of fitness across individual assays. In many cases, the known genotypic polymorphisms alone were not sufficient to accurately predict the virus’ phenotype. Therefore, we conclude that comprehensive risk analyses based on surveillance of circulating influenza virus strains are necessary to assess the potential for human infection by emerging influenza A viruses.
    Emerging Microbes and Infections. 11/2013;
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    ABSTRACT: Background. High mortality and uncertainty about the effectiveness of neuraminidase inhibitors (NAIs) in humans infected with A (H7N9) influenza viruses are public health concerns.Methods. Susceptibility of N9 viruses to NAIs was determined in a fluorescence-based assay. The NAI oseltamivir (5, 20, or 80 mg/kg/day) was administered to BALB/c mice twice daily starting 24, 48, or 72 hours after A/Anhui/1/2013 (H7N9) virus challenge.Results. All 12 avian N9 and 3 human H7N9 influenza viruses tested were susceptible to NAIs. Without prior adaptation, A/Anhui/1/2013 (H7N9) caused lethal infection in mice that was restricted to the respiratory tract and resulted in pulmonary edema and acute lung injury with hyaline membrane formation, leading to decreased oxygenation, all characteristics of human acute respiratory distress syndrome. Oseltamivir at 20 and 80 mg/kg protected 80% and 88% of mice when initiated after 24 hours, and the efficacy decreased to 70% and 60%, respectively, when treatment was delayed by 48 hours. Emergence of oseltamivir-resistant variants was not detected.Conclusions. H7N9 viruses are comparable to currently circulating influenza A viruses in susceptibility to NAIs. Based on these animal studies, early treatment is associated with improved outcomes.
    The Journal of Infectious Diseases 10/2013; · 5.85 Impact Factor
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    ABSTRACT: Recently, novel H7N9 influenza viruses have caused an unprecedented outbreak in humans. Pigs are an important intermediate host for influenza; thus we assessed the replication ability of three human H7N9 viruses (A/Anhui/1/2013, A/Shanghai/1/2013, A/Shanghai/2/2013) in swine tissue explants. All viruses tested replicated efficiently in tracheas and bronchi of the explants, with limited replication in alveolar cells. Swine respiratory tissue explants can serve as an efficient model for screening replication potential of newly emerging H7N9 viruses.
    Journal of Virology 09/2013; · 5.08 Impact Factor
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    ABSTRACT: Human infection with avian influenza A(H9N2) virus was identified in Bangladesh in 2011. Surveillance for influenza viruses in apparently healthy poultry in live-bird markets in Bangladesh during 2008-2011 showed that subtype H9N2 viruses are isolated year-round, whereas highly pathogenic subtype H5N1 viruses are co-isolated with subtype H9N2 primarily during the winter months. Phylogenetic analysis of the subtype H9N2 viruses showed that they are reassortants possessing 3 gene segments related to subtype H7N3; the remaining gene segments were from the subtype H9N2 G1 clade. We detected no reassortment with subtype H5N1 viruses. Serologic analyses of subtype H9N2 viruses from chickens revealed antigenic conservation, whereas analyses of viruses from quail showed antigenic drift. Molecular analysis showed that multiple mammalian-specific mutations have become fixed in the subtype H9N2 viruses, including changes in the hemagglutinin, matrix, and polymerase proteins. Our results indicate that these viruses could mutate to be transmissible from birds to mammals, including humans.
    Emerging Infectious Diseases 09/2013; 19(9). · 6.79 Impact Factor
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    ABSTRACT: In aquatic birds, influenza A viruses mainly replicate in the intestinal tract without significantly affecting the health of the host, but in mammals they replicate in the respiratory tract and often cause disease. Occasionally, influenza viruses have been detected in stool samples of hospitalized patients and in rectal swabs of naturally or experimentally infected mammals. In this study, we compared the biological and molecular differences among four wild-type avian H1N1 influenza viruses and their corresponding fecal and lung isolates in DBA/2J and BALB/cJ mice. All fecal and lung isolates were more pathogenic than the original wild-type viruses, when inoculated into mice of both strains. The increased virulence was associated with the acquisition of genetic mutations. Most of the novel genotypes emerged as PB2(E627K) or HA(F128V, F454L, or H300P) variants, and double-mutants frequently occurred in the same isolate. However, influenza strain- and host-specific differences were also observed in terms of selected variants. The avian H1N1 virus of shorebird origin appeared to be unique in its ability to rapidly adapt to BALB/cJ mice via the fecal route, compared to the adaptability of the H1N1 virus of mallard origin. Furthermore, bimodal distribution was observed in fecal shedding in mice infected with the fecal isolates, while normal distribution was observed after infection with the lung isolates or wild-type virus. Fecal isolates contained HA mutations that increased the activation pH of the HA protein. We conclude that influenza variants that emerge in fecal isolates in mammals might influence viral transmission, adaptation to mammals, and viral ecology or evolution.
    Journal of Virology 08/2013; · 5.08 Impact Factor
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    ABSTRACT: A novel H7N9 influenza A virus first detected in March 2013 has since caused more than 130 human infections in China, resulting in 40 deaths. Preliminary analyses suggest that the virus is a reassortant of H7, N9 and H9N2 avian influenza viruses, and carries some amino acids associated with mammalian receptor binding, raising concerns of a new pandemic. However, neither the source populations of the H7N9 outbreak lineage nor the conditions for its genesis are fully known. Using a combination of active surveillance, screening of virus archives, and evolutionary analyses, here we show that H7 viruses probably transferred from domestic duck to chicken populations in China on at least two independent occasions. We show that the H7 viruses subsequently reassorted with enzootic H9N2 viruses to generate the H7N9 outbreak lineage, and a related previously unrecognized H7N7 lineage. The H7N9 outbreak lineage has spread over a large geographic region and is prevalent in chickens at live poultry markets, which are thought to be the immediate source of human infections. Whether the H7N9 outbreak lineage has, or will, become enzootic in China and neighbouring regions requires further investigation. The discovery here of a related H7N7 influenza virus in chickens that has the ability to infect mammals experimentally, suggests that H7 viruses may pose threats beyond the current outbreak. The continuing prevalence of H7 viruses in poultry could lead to the generation of highly pathogenic variants and further sporadic human infections, with a continued risk of the virus acquiring human-to-human transmissibility.
    Nature 08/2013; · 38.60 Impact Factor
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    ABSTRACT: Since the end of March 2013, avian a influenza viruses of the H7N9 subtype have caused more than 130 human cases of infection in China, many of which were severe, resulting in 43 fatalities. Although this A(H7N9) virus outbreak is now under control, the virus (or one with similar properties) could reemerge as winter approaches. To better assess the pandemic threat posed by A(H7N9) viruses, NIAID/NIH Centers of Excellence in Influenza Research and Surveillance (CEIRS) investigators and other expert laboratories in China and elsewhere have characterized the wild-type avian A(H7N9) viruses in terms of host range, virulence, and transmission, and are evaluating the effectiveness of antiviral drugs and vaccine candidates. However, to fully assess the potential risk associated with these novel viruses, there is a need for additional research including experiments that may be classified as "gain-of-function" (GOF). Here, we outline the aspects of the current situation that most urgently require additional research, our proposed studies, and risk-mitigation strategies.
    Science 08/2013; · 31.20 Impact Factor
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    ABSTRACT: Wild birds have been implicated in the emergence of human and livestock influenza. The successful prediction of viral spread and disease emergence, as well as formulation of preparedness plans have been hampered by a critical lack of knowledge of viral movements between different host populations. The patterns of viral spread and subsequent risk posed by wild bird viruses therefore remain unpredictable. Here we analyze genomic data, including 287 newly sequenced avian influenza A virus (AIV) samples isolated over a 34-year period of continuous systematic surveillance of North American migratory birds. We use a Bayesian statistical framework to test hypotheses of viral migration, population structure and patterns of genetic reassortment. Our results reveal that despite the high prevalence of Charadriiformes infected in Delaware Bay this host population does not appear to significantly contribute to the North American AIV diversity sampled in Anseriformes. In contrast, influenza viruses sampled from Anseriformes in Alberta are representative of the AIV diversity circulating in North American Anseriformes. While AIV may be restricted to specific migratory flyways over short time frames, our large-scale analysis showed that the long-term persistence of AIV was independent of bird flyways with migration between populations throughout North America. Analysis of long-term surveillance data provides vital insights to develop appropriately informed predictive models critical for pandemic preparedness and livestock protection.
    PLoS Pathogens 08/2013; 9(8):e1003570. · 8.14 Impact Factor
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    ABSTRACT: H9N2 avian influenza viruses continue to spread in poultry and wild birds throughout Eurasia. To characterize H9N2 influenza viruses from pheasants, quail, and white-bellied bustards (WBBs) used to train falcons in the United Arab Emirates (UAE). Four H9N2 viruses were isolated from pheasants, quail, and WBB used for falconry in the UAE, and antigenic, molecular, phylogenetic analysis, and invivo characterization of H9N2 viruses were performed. The pheasant and WBB isolates were antigenically and molecularly clearly related and along with the quail isolates contained multiple "avian-human" substitutions. The release of smuggled H9N2-infected birds for falconry may contribute to the spread of these viruses to wild birds, domestic poultry, and humans.
    Influenza and Other Respiratory Viruses 07/2013; · 1.47 Impact Factor
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    ABSTRACT: Despite the use of vaccines, low-pathogenic (LP) H5N2 influenza viruses have continued to circulate and evolve in chickens in Mexico since 1993, giving rise to multiple genetic variants. Antigenic drift is partially responsible for the failure to control H5N2 influenza by vaccination; the contribution of maternal antibodies to this problem has received less attention. We investigated the effect of different antisera on the efficacy of vaccination and whether booster doses of vaccine can impact immune suppression. While single doses of inactivated oil emulsion vaccine to currently circulating H5N2 influenza viruses provide partial protection from homologous challenge, chickens that receive high-titer homologous antisera intraperitoneally before vaccination showed effects ranging from added protection to immunosuppression. Post-infection antisera were less immunosuppressive than antisera obtained from field-vaccinated chickens. Homologous, post-infection chicken antisera provided initial protection from virus challenge, but reduced the induction of detectable antibody responses. Homologous antisera from field-vaccinated chickens were markedly immunosuppressive, annulling the efficacy of the vaccine and leaving the chickens as susceptible to infection as non-vaccinated birds. Booster doses of vaccine reduced the immunosuppressive effects of the administered sera. Vaccine efficacy against LP H5N2 in Mexico can be severely reduced by maternal antibodies. Source-dependent antisera effects offer the possibility of further elucidation of the immunosuppressive components involved.
    Influenza and Other Respiratory Viruses 07/2013; · 1.47 Impact Factor
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    ABSTRACT: We previously reported that A/swine/Korea/1204/2009(H1N2) virus was virulent and transmissible in ferrets in which the respiratory droplet'transmissible virus (CT-Sw/1204) had acquired simultaneous HAD225G and NAS315N mutations. Incorporating these mutations into the non-pathogenic A/swine/Korea/1130/2009(H1N2, Sw/1130) virus consequently altered pathogenicity and growth in animal models but could not establish efficient transmission or remarkable disease. We, therefore, exploited various reassortants of these two viruses to better understand and identify other viral factors responsible for pathogenicity, transmissibility, or both. We found that possession of the CT-Sw/1204 tripartite viral polymerase enhanced replicative ability and pathogenicity in mice more significantly than did individual expression of polymerase subunit proteins. In ferrets, homologous expression of viral RNA polymerase complex genes in the context of the mutant Sw/1130 carrying the HA225G and NA315N modifications induced optimal replication in the upper nasal and lower respiratory tracts and also promoted efficient aerosol transmission to respiratory droplet'contact ferrets. These data show that the synergistic function of the tripartite polymerase gene complex of CT-Sw/1204 is critically important for virulence and transmission independent of the surface glycoproteins. Sequence comparison results reveal putative differences that are likely to be responsible for variation in disease. Our findings may help elucidate previously undefined viral factors that could expand the host range and disease severity induced by triple-reassortant swine viruses, including the A(H1N1)pdm09 virus, and therefore further justify the ongoing development of novel antiviral drugs targeting the viral polymerase complex subunits.
    Journal of Virology 07/2013; · 5.08 Impact Factor

Publication Stats

34k Citations
3,338.59 Total Impact Points


  • 2013
    • United Arab Emirates University
      • Veterinary Research Laboratory
      Al ‘Ayn, Abu Zaby, United Arab Emirates
  • 2012–2013
    • Erasmus MC
      • Department of Virology
      Rotterdam, South Holland, Netherlands
    • The Scripps Research Institute
      La Jolla, California, United States
    • University of Georgia
      • Department of Population Health
      Athens, GA, United States
    • United States Geological Survey
      Reston, Virginia, United States
  • 2005–2013
    • Chungbuk National University
      • • Department of Microbiology
      • • College of Medicine and Medical Research Institute
      Tyundyu, North Chungcheong, South Korea
    • Centers for Disease Control and Prevention
      Atlanta, Michigan, United States
    • National Institute of Veterinary Research, Vietnam
      Hà Nội, Ha Nội, Vietnam
  • 1996–2013
    • The University of Hong Kong
      • • Centre of Influenza Research
      • • Department of Microbiology
      • • Li Ka Shing Faculty of Medicine
      Hong Kong, Hong Kong
  • 2010–2012
    • University of Alberta
      • Department of Biological Sciences
      Edmonton, Alberta, Canada
    • Korea Research Institute of Bioscience and Biotechnology KRIBB
      Anzan, Gyeonggi Province, South Korea
    • University of Bologna
      • School of Agriculture and Veterinary Medicine
      Bologna, Emilia-Romagna, Italy
  • 2009–2012
    • Mahidol University
      • Faculty of Veterinary Science
      Bangkok, Bangkok, Thailand
  • 2003–2012
    • Shantou University
      • • International Institute of Infection and Immunity
      • • Department of Microbiology and Immunology
      Swatow, Guangdong, China
    • United States Department of Agriculture
      • Agricultural Research Service (ARS)
      Washington, D. C., DC, United States
    • Chumakov Institute of Poliomyelitis and Viral Encephalitides
      Moskva, Moscow, Russia
  • 2002–2012
    • Ivanovsky Institute of Virology
      Moskva, Moscow, Russia
    • Philipps-Universität Marburg
      • Institut für Virologie
      Marburg, Hesse, Germany
  • 1972–2012
    • St. Jude Children's Research Hospital
      • Department of Infectious Diseases
      Memphis, TN, United States
    • National Institutes of Health
      Maryland, United States
  • 1993–2009
    • University of Tennessee
      • • Department of Pathology
      • • Division of Biostatistics and Epidemiology
      Knoxville, Tennessee, United States
    • Le ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec
      Québec, Quebec, Canada
  • 2007
    • National Veterinary Research Quarantine Service
      Sŏul, Seoul, South Korea
    • The University of Memphis
      Memphis, Tennessee, United States
  • 2004
    • MRC National Institute for Medical Research
      Londinium, England, United Kingdom
    • Tai Lung Veterinary Laboratory
      Hong Kong, Hong Kong
    • Chungnam National University
      • College of Veterinary Medicine
      Seongnam, Gyeonggi, South Korea
  • 1997–2004
    • Istituto Superiore di Sanità
      Roma, Latium, Italy
  • 1999
    • University of Wisconsin, Madison
      • Department of Pathobiological Sciences
      Mississippi, United States
    • Emory University
      Atlanta, Georgia, United States
    • Queen Mary Hospital
      Hong Kong, Hong Kong
  • 1966–1999
    • Australian National University
      Canberra, Australian Capital Territory, Australia
  • 1998
    • University of Virginia
      • Division of Maternal Fetal Medicine
      Charlottesville, Virginia, United States
  • 1994–1998
    • Erasmus Universiteit Rotterdam
      • Department of Virology
      Rotterdam, South Holland, Netherlands
    • Hokkaido University
      • • Laboratory of Microbiology
      • • Graduate School of Veterinary Medicine
      Sapporo-shi, Hokkaido, Japan
    • The Commonwealth Scientific and Industrial Research Organisation
      Canberra, Australian Capital Territory, Australia
  • 1993–1997
    • University of Massachusetts Medical School
      • Department of Pathology
      Worcester, MA, United States
  • 1990–1993
    • University of Otago
      • Virus Research Unit
      Taieri, Otago Region, New Zealand
  • 1991
    • University of Melbourne
      • Department of Microbiology and Immunology
      Melbourne, Victoria, Australia
  • 1985–1990
    • University of Alabama at Birmingham
      • Department of Microbiology
      Birmingham, AL, United States
  • 1988
    • University of Louisville
      • Department of Microbiology and Immunology
      Louisville, KY, United States
  • 1987
    • Georgia Poultry Laboratory Network
      Georgia, United States
  • 1985–1987
    • National Institute for Biological Standards and Control
      • Division of Virology
      Potters Bar, England, United Kingdom
  • 1981
    • University of Guelph
      Guelph, Ontario, Canada