avian to human H9N2 flu

avian to human H9N2 flu - Avian-to-human transmission of...

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Avian-to-human transmission of H9N2 subtype influenza A viruses: Relationship between H9N2 and H5N1 human isolates Y. P. Lin* ² , M. Shaw , V. Gregory ² , K. Cameron ² , W. Lim § , A. Klimov , K. Subbarao , Y. Guan i , S. Krauss , K. Shortridge i , R. Webster , N. Cox , and A. Hay ² ² Division of Virology, National Institute for Medical Research, Mill Hill, London, NW7 1AA, United Kingdom; § Government Virus Unit, Queen Mary Hospital, Hong Kong SAR, People’s Republic of China; Influenza Branch, Division of Viral and Rickettsial Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333; Department of Virology and Molecular Biology, St. Jude Children’s Research Hospital, Memphis, TN 38105; and i Microbiology Department, University of Hong Kong, University Pathology Building, Queen Mary Hospital, Hong Kong SAR, People’s Republic of China Contributed by R. Webster, June 13, 2000 In 1997, 18 cases of influenza in Hong Kong (bird flu) caused by a novel H5N1 (chicken) virus resulted in the deaths of six individuals and once again raised the specter of a potentially devastating influenza pandemic. Slaughter of the poultry in the live bird markets removed the source of infection and no further human cases of H5N1 infection have occurred. In March 1999, however, a new pandemic threat appeared when influenza A H9N2 viruses infected two children in Hong Kong. These two virus isolates are similar to an H9N2 virus isolated from a quail in Hong Kong in late 1997. Although differing in their surface hemagglutinin and neur- aminidase components, a notable feature of these H9N2 viruses is that the six genes encoding the internal components of the virus are similar to those of the 1997 H5N1 human and avian isolates. This common feature emphasizes the apparent propensity of avian viruses with this genetic complement to infect humans and high- lights the potential for the emergence of a novel human pathogen. R ecurrent epidemics of influenza are fairly predictable annual events. In contrast, the future occurrence of a pandemic, caused by the emergence of a novel influenza A subtype against which the population has little or no immunity, is unpredictable as to timing or identity of the prospective agent. Influenza A viruses of aquatic birds comprise a diverse mix of antigenic subtypes [including 15 hemagglutinin (HA) and 9 neuraminidase (NA) subtypes] and represent a large reservoir y source of novel antigens to which the human population is naı¨ve (1, 2). The high species specificity of these viruses restricts transmission to mammalian species to a relatively rare event and only a few subtypes have circulated in mammalian species for extended periods. The conse- quences of interspecies transmission can be devastating. For exam- ple, an epizootic in harbor seals on the east coast of the U.S. in 1980 caused by an H7N7 virus resulted in mortality of some 600 seals (3).
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This note was uploaded on 07/12/2011 for the course BIO 620 taught by Professor Hardy during the Spring '11 term at University of Florida.

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avian to human H9N2 flu - Avian-to-human transmission of...

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