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Avian Influenza

Avian Influenza is a highly contagious viral disease affecting the respiratory, digestive, and/or nervous system of many species of birds. It is caused by a Type A influenza virus. There are two types of avian influenza virus, low pathogenicity (LPAI) and high pathogenicity (HPAI). Wild birds are the natural hosts for the virus. Avian flu viruses circulate among birds worldwide and are highly contagious among birds. Human cases of Avian Influenza have been reported among persons who handled affected poultry. In rare cases outside of the United States, some instances of human infection have resulted in death. If transmission of Avian Influenza from human to human begins and is sustained, a pandemic may result because most humans will not have antibodies to the new strain. Coordination between the Department of Agriculture and the Department of Public Health is critical to assure effective implementation of response activities and control measures.

An avian influenza outbreak will require the use of much of the same infrastructure as that needed for response to other disasters in Illinois. Many local, State, and Federal agencies have developed emergency response plans, some of which apply to avian influenza contingencies. Effective response to a large-scale avian influenza outbreak will not only require the combined resources of various agencies, but the ability to deliver the support quickly.

Overview of Influenza

  • Avian Influenza is a subtype of the Type A influenza virus. 
    • Wild birds are natural hosts of the virus, hence the name avian influenza or bird flu.             
    • The virus circulates among birds worldwide.
    • Virtually all of the possible influenza subtypes exist among wild waterfowl.
    • Waterfowl usually show little if any signs and it can be deadly to domesticated birds, like chickens.
    • 15 subtypes classified as H
    • 9 subtypes classified as N
    • Distinguished by differences in their genetic structures
    • High pathogenic strain in poultry is H5N1
    • The following subtypes are usually found in humans H1N1, H1N2, H2N2, H3N2.
  • Reassortment of the influenza virus occurs when 2 different subtypes are present in the same animal.  Influenza virus has the ability to change its molecular antigenic structure making previously immune animals susceptible.
  • Avian influenza is also designated:
    • High pathogenic  (high path) means very high mortality among poultry
    • Low pathogenic (low path) very low mortality among chickens.
    • This is determined through bird testing
  • Low path AI with continued spread among chickens can mutate to high path AI.
  • In the US majority of low path AI infections come from live bird markets where commingling of poultry and waterfowl and/or contamination from waterfowl fecal material can occur.

 Sources of Infection

  • Migratory water fowl
  • Intentional contamination
  • Birds illegally imported into the US
    • Fighting birds           
    • Pet birds
    • Fancy chickens
  • It spreads among birds through nasal and eye secretions and manure. 
  • The virus can also be spread by equipment, vehicles, egg flats, crates and people whose clothing or shoes come in contact with the virus.


  • This virus is easily killed with routine disinfectants
  • Poultry producers in Illinois need to use normal bio-security procedures to prevent an outbreak:
    • Notify veterinarian of any suspected disease.
    • Stay informed about the health of neighboring animals.
    • Do not move birds from farm to farm.
    • Keep flock away from wild birds.
    • Be sure the flock has no contact with contaminated animals.
    • Isolate new birds.
    • Restrict unauthorized people and vehicles from the farm.
    • Disinfect tires, equipment and clothing when going on and off the farm.
    • Quarantine contaminated areas and flocks immediately.
    • Dispose of dead birds properly.
    • Although there are vaccines available, there is not a vaccine that covers all 15 strains of the disease. Therefore, since there is no way to determine which strain will infect a flock, vaccines are generally not practical to prevent infection.
    • Practice heightened security in the live bird markets.   
      • 7 known locations in Chicago
      • Consumer Safety Officer from Bureau of Meat and Poultry to markets with recommendations on safe handling of birds
      • Leaving handout/poster to provide information
      • Continued contacts as needed


  • Reportable disease (Illinois Diseased Animal Act)
  • Testing of poultry presented to Animal Disease Laboratories (Galesburg and Centralia)
  • Knowingly bringing either infected poultry or materials into IL is now a felony.

 Illinois Avian Influenza Plan

  • Quarantine facilities under the Illinois Diseased Animal Plan
  • Quarantine areas surrounding affected flocks
  • Testing of flocks in surrounding areas to determine possible exposure
  • Depopulation of affected and exposed flocks
  • Coordinate with poultry industry and private


  • NPIP (National Poultry Improvement Plan) registered flocks
  • Live bird markets (7 known in Cook County)
    • Poster
    • Visiting and educations by Meat and Poultry
  • Commercial producers
  • Licensed egg producers       

 The following is excerpted from Pro-med 10-24-05:

 Very low risk to human health from A/H5N1 avian influenza in Europe according to ECDC risk assessment

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The direct risk to the health of people in Europe from the avian influenza detected in Romania and Turkey is very low, according to experts from the European Centre for Disease Prevention and Control (ECDC). The risk is almost entirely confined to people living on farms with infected poultry or workers involved with culling (killing) and disposal of infected birds.

There has been considerable confusion in the media about the arrival of avian influenza A/H5N1 into bird flocks in Europe and the arrival of pandemic influenza. Not only could this confusion cause unnecessary anxiety and fear of harmless wild birds, it could undermine efforts to prepare for a pandemic, as a pandemic may not occur for several years and may not be caused by H5N1 avian influenza at all. There are many other candidate human and animal influenza strains. 

Freqently Asked Questions: Avian Influenza
Questions and Answers: Avian Influenza
Biosecurity for the Birds
USDA - Avian Influenza
Illinois Department of Public Health - Avian Influenza

Questions or comments.

Copyright © 2001
State of Illinois Department of Agriculture
P.O. Box 19281, State Fairgrounds
Springfield, IL 62794-9281
(217) 782-2172
(217) 524-6858 TTY