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Avian Influenza - Bird Flu

Last updated May 3, 2018

Approved by: Krish Tangella MD, MBA, FCAP

Image showing the different sites of infection (shown in red) of seasonal H1N1 versus avian H5N1 influences their lethality and ability to spread.


What are the other Names for this Condition? (Also known as/Synonyms)

  • Fowl Plague
  • H5N1 Avian Influenza
  • Human Pathogenic Avian Influenza (HPAI)

What is Avian Influenza - Bird Flu? (Definition/Background Information)

  • Avian Influenza is a mildly to severely infectious viral disease that affects birds and is caused by the influenza virus A, subtypes H5, H7, and H9. When birds are infected with an attack of flu, the condition is termed as Avian Influenza or Bird Flu
  • Influenza virus A is present worldwide in the intestines of wild birds (waterfowls) without causing them any harm. But, when this virus infects domesticated birds (such as chicken, ducks, pigeons) through contact with infected poultry, dirty cages, infected secretions/food/water, it can make the birds very sick and kill them
  • The risks of infection to humans from such birds are generally low, or occur only occasionally. The bird infection can be transmitted  to humans through:
    • Inhalation of virus from nose, mouth
    • Oral ingestion of infected food or water
    • Direct contact with secretions of the infected birds, like their feces, nasal secretions, and saliva
    • Direct contact with the infected  bird
  • In humans the infection can be mild, severe, and/or potentially fatal, depending on the influenza subtype

Who gets Avian Influenza - Bird Flu? (Age and Sex Distribution)

Any individual is susceptible to Avian Influenza; though, the following groups are more likely to be affected by the condition:

  • Farmers, who may have direct/regular contact with the birds
  • Poultry workers
  • Individuals, who are prone to come in direct contact with infected birds
  • Those who eat raw and/or undercooked meat and egg of infected birds
  • Travelers, who go on tour to countries affected by the infectious disease (specifically parts of Asia and northeast Africa)

What are the Risk Factors for Avian Influenza - Bird Flu? (Predisposing Factors)

The following groups of individuals have a higher risk of contracting Avian Influenza - Bird Flu:

  • Farmers, farm workers in direct contact with the domesticated birds
  • Poultry farm workers, cleaners
  • Those who come into direct/close contact with infected birds (dead or alive), or during the disposal (improper) of dead/infected birds
  • Individuals, who eat raw and/or undercooked meat and eggs of infected birds
  • Travelers to infected regions (parts of Asia and northeast Africa), or countries with known cases of the infectious disease spread

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Avian Influenza - Bird Flu? (Etiology)

  • Bird Flu is caused by the influenza virus belonging to subtypes H5, H7, and H9. Thus the Avian Influenza subtypes are termed as: H5N1 (most common and severe), H7N7, and H9N2
  • In birds, the infection affects the respiratory system. Transmission of the disease to humans, occur through close contact with the infected live/dead birds
  • Spread of infection from one individual to another has not been generally observed.

Following factors influence the transmission of infection to humans:

  • Movement of the birds
  • Secretions of infected birds, like their droppings, saliva
  • Wind direction
  • Direct contact with the infected birds

What are the Signs and Symptoms of Avian Influenza - Bird Flu?

Avian Influenza (commonly H5N1 Influenza) can cause severe infection in humans. Signs and symptoms manifested by the disease are:

  • Diarrhea
  • Cough
  • Breathing difficulty
  • High fever
  • Headache, muscle aches
  • Weakness
  • Running nose, sore throat

How is Avian Influenza - Bird Flu Diagnosed?

The following tests may be performed for diagnosing Avian Influenza:

  • Physical exam and evaluation of medical history
  • Auscultation test; a test used to check abnormal sounds while breathing
  • Chest x-ray
  • Nasopharyngeal culture
  • White blood cell differential
  • Other tests may be performed to check the proper functioning of the heart, lungs, liver, and kidneys

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Avian Influenza - Bird Flu?

Complications that may be caused by Avian Influenza include:

  • Severe breathing problems, or acute respiratory distress
  • Failure of the important organs in the body
  • Pneumonia
  • Eye infections
  • Sepsis

How is Avian Influenza - Bird Flu Treated?

Treatments may vary depending on the type of Avian Flu virus causing the disease. Treatment procedure includes:

  • Antiviral medications to reduce the effect of the symptoms are recommended; these include oseltamivir, zanamivir
  • Use of breathing machine (medical ventilator) is advised for those having severe infection
  • Studies have shown that routine flu shots (given against seasonal influenza/flu virus) do not give protection against the viral infection. However, as a general precautionary measure, individuals should take flu shots as preventative steps, for maintaining better health

Current studies have shown that person-to-person transmission of Bird Flu virus is not very common. However, the potential for a person-to-person transmission is a very real threat to the community, which may result in a world pandemic of Bird Flu viral infection. Given such a grave concern and the fact that Avian Influenza is a highly infectious disease, the affected individuals should be separated from others and given necessary treatment.

How can Avian Influenza - Bird Flu be Prevented?

Currently, no vaccine is available to prevent Avian Influenza. The normal influenza vaccine does not offer protection against the Bird Flu virus.

Avian Influenza prevention would have to include the following safety precautions:

  • Avoiding visiting live bird markets, especially in places where there is an Avian Flu outbreak
  • Individuals, who come in direct/close contact with birds due to their occupation, should always use protective clothing and special breathing masks
  • Eating undercooked or uncooked meat and animal products should be avoided
  • Proper personal hygiene (like hand-washing, covering mouth and nose) and environmental hygiene should be maintained

What is the Prognosis of Avian Influenza - Bird Flu? (Outcomes/Resolutions)

  • The severity of the infection is a deciding factor in the prognosis, and this depends on the Avian Influenza subtype H5N1, H7N9, and H9N2. Death is a possibility in some cases
  • The most common subtype - H5N1, is severe, highly infectious, and has a high mortality rate of about 60% (per WHO)

Additional and Relevant Useful Information for Avian Influenza - Bird Flu:

  • Animals and birds carrying influenza virus are known to sometimes pose a threat to humans, who come in close contact with the infected creatures and contaminated environment. Such infections acquired from animal sources are termed, zoonotic infections
  • In addition to Avian Influenza, the WHO has reported swine influenza (subtypes H1N1 and H3N2). Interaction of viruses between animals and humans are not yet completely understood; more so, because there seems to be the involvement of some genetic component

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Dec. 9, 2013
Last updated: May 3, 2018