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Introduction to Avian Influenza David L Suarez D V M Ph D Research Leader Exotic and Emerging Avian Viral Disease Research Unit Agricultural Research Service United States Department of Agriculture Influenza A Virus Negative sense RNA Single stranded Segmented Neuraminidase Hemagglutinin M2 PB1 PB2 PA HA NP NA MA NS M1 16 Hemagglutinin subtypes 9 Neuraminidase Subtypes Influenza Nomenclature A Chicken Pennsylvania 1370 83 H5N2 1 2 3 4 5 6 7 1 Antigenic type 2 Isolate host of origin 3 Geographic location 4 Isolate reference 5 Year of isolation 6 Hemagglutinin subtype 7 Neuraminidase subtype Influenza Subtypes 16 Hemagglutinin subtypes 9 Neuraminidase subtypes 2 Nonstructural subtypes Can occur in any combination Useful for epidemiology What Defines a Subtype Neutralizing antibody produced against one virus will neutralize all other viruses of the same subtype A different subtype is defined when neutralizing antibody produced for one subtype will not neutralize viruses from other subtypes Subtypes are defined by antigenic characteristics of the virus Virus isolates will occasionally cross react with more than one reference antibodies Hemagglutination inhibition tests provide a simple way to measure subtype differences Natural Ecology of Avian Influenza Mallards Blue Wing Teal Herring Gulls Avian Influenza is naturally found in wild birds Virus infection is not normally thought to cause disease in its natural host Viruses are low pathogenic Wild bird surveys have shown certain duck gull and shorebirds species are commonly infected at different times of the year All type A influenza viruses are thought to originate from wild birds Isolation of Avian Influenza from Different Bird Species Most isolations from Anseriformes ducks geese and swans and Charadriiformes gulls terns plovers surfbirds sandpipers puffins Within Anseriformes highest isolation rates from Mallards and other dabbling ducks Isolations of virus from many other Orders of birds ex loons grebes shearwaters



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