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Tucson Audubon Society Many of us worry about avian influenza and its effect on bird and human life. On Nov. 4, 2005, the University of Georgia’s Department of Population Health College of Veterinary Medicine released its Southeastern Cooperative Wildlife Disease Study which answers some of our questions. What are avian influenza viruses (AIV)? Type A influenza viruses associated with avian species. The movement and adaptation of Type AIV from wild birds to new host species (especially mammals) is not a common event. What is a highly pathogenic avian influenza (HPAI) virus? Influenza viruses that cause high mortality in domestic poultry and are associated with the H5 and H7 subtypes. What is "Bird Flu" and what is "HPAI H5N1"? "Bird Flu" is a nonscientific term coined to describe HPAI H5N1 viruses present in Asia since 1997. This term has caused a great deal of confusion because it is often used as a synonym for avian influenza. HPAI H5N1 is a highly-pathogenic H5N1 virus. In 1997, a human death resulting from HPAI H5N1 virus infection in Hong Kong was reported; there have been over 100 human cases (all in Asia) with approximately 60 fatalities since that time. What do we know about avian influenza viruses in wild birds? Most AIVs have been isolated from birds that are associated with water, with most isolations originating from species in the Anseriformes (ducks, geese, and swans) and Charadriiformes (gulls, terns, and shorebirds). In ducks, the prevalence of AIV peaks in late summer and early fall. In gulls and shorebirds, peak infection rates are associated with spring migration but these rates differ greatly between species and are generally low. No naturally-occurring North American AIVs from wild birds have been associated with mortality or morbidity in any wild bird species. There is no indication that any HPAI viruses exist in North American wild bird populations. Is HPAI H5N1 present in North America? There is no evidence to suggest that an HPAI H5N1 virus is present anywhere in North America. Is there currently a public health risk associated with HPAI H5N1 in wild birds? There currently is no recognized public health risk in the U.S. associated with wild bird contact. There has never been a single documented case of avian influenza virus transmission directly from wild birds to humans. Is there a domestic animal health risk associated with HPAI in wild birds? There are no documented cases of HPAI transmission from a wild bird to domestic birds in the U.S. In Asia, the recent expansion in distribution of HPAI H5N1 suggests that domestic flocks are being infected with this virus through contact with migratory wild birds. What is the possibility of HPAI H5N1 entering North America via migratory wild birds? There is very limited exchange of AIVs between continents (even with very common influenza viruses). It is not possible to discount the possibility of an HPAI H5N1 introduction, but such an event based on the known epidemiology of other avian influenza viruses would likely be a very low probability event. What is the possibility of this virus being maintained in wild bird populations? Experimental studies have demonstrated bird-to-bird transmission of HPAI H5N1 in mallards, but these studies were completed under confinement conditions that are not representative of natural conditions. Information on environmental persistence of HPAI H5N1 in water is lacking. Is there surveillance for HPAI H5N1 in the United States? Surveillance for AIV was taking place in the United States and other North American countries prior to the emergence of HPAI H5N1. Wild bird surveillance has and will be expanded to include larger geographic areas and areas of potential introduction, such as Alaska. Additional information on HPAI can be found at: Southeastern Cooperative Wildlife Disease Study: www.uga.edu/scwds/avianinfluenzainformation.html The Centers for Control and Prevention: www.cdc.gov/flu/avian USDA-APHIS-Veterinary Services: www.aphis.usda.gov/lpa/issues/avian_influenza/index.html USGS National Wildlife Health Center: www.nwhc.usgs.gov/research/avian_influenza/avian_influenza.html
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