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Avian Influenza

Background

Avian influenza (AI), or bird flu, is a group of viruses that affect wild and domestic birds. The viruses are only found in a small number of birds in the wild, usually waterfowl and shorebirds, and rarely cause disease in these birds. The viruses are transmitted in fecal droppings, saliva, and nasal discharges.

Mallards

Since 2003, a virulent form of AI has emerged in Southeast Asia, and now has been detected throughout Asia, parts of Europe, and parts of Africa. This highly pathogenic avian influenza (HPAI) H5N1 virus has resulted in the deaths of millions of domestic poultry, most euthanized to prevent spread.

As of August 2007, there have been over 300 human cases of highly pathogenic H5N1 reported (primarily in Asia), of which approximately 60% have been fatal. The actual number of human cases and fatalities due to H5N1 is low when compared to the 36,000 deaths annually just in the U.S. from human influenza viruses, but has caused concern due to the high death rate in those people who are sick with H5N1. Additionally, there is worry that with human infection, the H5N1 virus could evolve by mutation or by obtaining genetic material from human influenza strains, and then human-to-human transmission could cause a worldwide influenza pandemic. Currently most human H5N1 infections are thought to be from close contact with infected poultry or contaminated materials, or by eating uncooked poultry products, not through wild bird to human transmission.

H5N1 has been detected and associated with deaths in wild birds in Asia and Europe. These findings and the continuing geographic spread of H5N1 have led to concern that migratory birds could carry this HPAI strain into North America. There is equal concern that illegal importation of poultry or poultry products, movements of infected captive wildlife, or infected people could introduce H5N1 to the U.S. To date, highly pathogenic H5N1 has not been detected in wild birds, domestic poultry, or humans in North America.

Due to the mixing of some species of wild birds from Asia and North America that occurs in the Alaskan region during the summer, U.S. sampling to detect H5N1 has focused on Alaska and the Pacific migratory bird flyway. Since 1998 more than 15,000 wild bird samples from Alaska have been analyzed and none have tested positive for highly pathogenic H5N1. Federal, state and university teams are continuing wild bird HPAI surveillance in Alaska and many other areas in North America, as outlined in a national plan, “An Early Detection System for Asian H5N1 HPAI in Wild Migratory Birds” (PDF, 1.6MB). Here in Wisconsin, the Department of Natural Resources (WDNR) and USDA-Wildlife Services are enhancing the state’s current surveillance program for HPAI by sampling approximately 2000 wild birds in the next year.

An important conservation concern is that some public and animal health officials will blame wild birds for spreading H5N1 and suggest culling wild birds as a control mechanism. As stated by the Food and Agriculture Organization of the United Nations (FAO), “Indiscriminate culling of wild migratory bird populations would be ineffective in preventing further spread of avian influenza.” The most effective way to prevent transmission of AI between wild birds and domestic poultry (and subsequent risk to humans) is to improve bio-security around poultry farms, preventing contact with wild birds. Wisconsin has emergency response plans (PDF, 548KB) in place if H5N1 or other highly pathogenic avian influenzas cause disease in the state’s wildlife, poultry, or public.

Additional Information

Related Sites

Avian Influenza Updates

Information on Avian Influenza and People

Information on Avian Influenza and Wild and Domestic Birds

Questions regarding Avian Influenza, please contact Wildlife Health

Questions for Wildlife Management

Last Revised: Wednesday October 17 2007