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Influenza in Migratory Birds and Evidence of Limited Intercontinental Virus Exchange
Scott Krauss 1, Caroline A. Obert2, John Franks1, David Walker1, Kelly Jones1, Patrick Seiler1, Larry Niles3, S. Paul Pryor4, John C. Obenauer2, Clayton W. Naeve2, Linda Widjaja5, Richard J. Webby1, Robert G. Webster1*
1 Division of Virology, Department of Infectious Diseases, St. Jude Children?s Research Hospital, Memphis, Tennessee, United States of America, 2 Hartwell Center for Bioinformatics and Biotechnology, St. Jude Children?s Research Hospital, Memphis, Tennessee, United States of America, 3 Conserve Wildlife Foundation, Bordentown, New Jersey, United States of America, 4 Environment Canada, Canadian Wildlife Service, Edmonton, Alberta, Canada, 5 Department of Structural Biology, St. Jude Children?s Research Hospital, Memphis, Tennessee, United States of America
Migratory waterfowl of the world are the natural reservoirs of influenza viruses of all known subtypes. However, it is unknown whether these waterfowl perpetuate highly pathogenic (HP) H5 and H7 avian influenza viruses. Here we report influenza virus surveillance from 2001 to 2006 in wild ducks in <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com
ffice:smarttags" /><st1:State w:st="on">Alberta</st1:State>, <st1:country-region w:st="on"><st1
lace w:st="on">Canada</st1lace></st1:country-region>, and in shorebirds and gulls at Delaware Bay (<st1:State w:st="on">New Jersey</st1:State>), <st1:country-region w:st="on"><st1lace w:st="on">United States</st1lace></st1:country-region>, and examine the frequency of exchange of influenza viruses between the Eurasian and American virus clades, or superfamilies. Influenza viruses belonging to each of the subtypes H1 through H13 and N1 through N9 were detected in these waterfowl, but H14 and H15 were not found. Viruses of the HP Asian H5N1 subtypes were not detected, and serologic studies in adult mallard ducks provided no evidence of their circulation. The recently described H16 subtype of influenza viruses was detected in American shorebirds and gulls but not in ducks. We also found an unusual cluster of H7N3 influenza viruses in shorebirds and gulls that was able to replicate well in chickens and kill chicken embryos. Genetic analysis of 6,767 avian influenza gene segments and 248 complete avian influenza viruses supported the notion that the exchange of entire influenza viruses between the Eurasian and American clades does not occur frequently. Overall, the available evidence does not support the perpetuation of HP H5N1 influenza in migratory birds and suggests that the introduction of HP Asian H5N1 to the <st1:country-region w:st="on">Americas</st1:country-region> by migratory birds is likely to be a rare event.
ffice:smarttags" /><st1:State w:st="on">Alberta</st1:State>, <st1:country-region w:st="on"><st1lace w:st="on">Canada</st1lace></st1:country-region>, and in shorebirds and gulls at Delaware Bay (<st1:State w:st="on">New Jersey</st1:State>), <st1:country-region w:st="on"><st1lace w:st="on">United States</st1lace></st1:country-region>, and examine the frequency of exchange of influenza viruses between the Eurasian and American virus clades, or superfamilies. Influenza viruses belonging to each of the subtypes H1 through H13 and N1 through N9 were detected in these waterfowl, but H14 and H15 were not found. Viruses of the HP Asian H5N1 subtypes were not detected, and serologic studies in adult mallard ducks provided no evidence of their circulation. The recently described H16 subtype of influenza viruses was detected in American shorebirds and gulls but not in ducks. We also found an unusual cluster of H7N3 influenza viruses in shorebirds and gulls that was able to replicate well in chickens and kill chicken embryos. Genetic analysis of 6,767 avian influenza gene segments and 248 complete avian influenza viruses supported the notion that the exchange of entire influenza viruses between the Eurasian and American clades does not occur frequently. Overall, the available evidence does not support the perpetuation of HP H5N1 influenza in migratory birds and suggests that the introduction of HP Asian H5N1 to the <st1:country-region w:st="on">Americas</st1:country-region> by migratory birds is likely to be a rare event. Citation: Krauss S, <st1lace w:st="on"><st1:City w:st="on">Obert</st1:City> <st1:State w:st="on">CA</st1:State></st1lace>, Franks J, Walker D, Jones K, et al. (2007) Influenza in migratory birds and evidence of limited intercontinental virus exchange. PLoS Pathog 3(11):e167. doi:10.1371/journal.ppat.0030167
lace w:st="on"><st1:City w:st="on">Obert</st1:City> <st1:State w:st="on">CA</st1:State></st1lace>, Franks J, Walker D, Jones K, et al. (2007) Influenza in migratory birds and evidence of limited intercontinental virus exchange. PLoS Pathog 3(11):e167. doi:10.1371/journal.ppat.0030167Full aticle at: http://pathogens.plosjournals.org/archive/1553-7374/3/11/pdf/10.1371_journal.ppat.0030167-L.pdf
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