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Avian influenza

Avian influenza A viruses cause the flu infection in birds. The viruses that cause the disease in birds can change (mutate) so it can spread to humans.


The first avian influenza in humans was reported in Hong Kong in 1997. It was called avian influenza (H5N1). The outbreak was linked to chickens.

Since then there have been human cases of avian influenza A in Asia, Africa, Europe, Indonesia, Vietnam, the Pacific, and the near East. Hundreds of people have become sick with this virus. Up to half of the people who get this virus die from the illness.

The chance of a worldwide outbreak in humans goes up the more the avian flu virus spreads.

Between December 15, 2014, and May 29, 2015 there have been more than 200 confirmed cases of birds infected with highly-pathogenic avian influenza (HPAI) H5 in the United States.

  • Most of these infections have occurred in both backyard and commercial poultry flocks.
  • These recent HPAI H5 viruses have not infected any people in the United States, Canada, or internationally. The risk of infection in people is low.

Your risk of getting the bird flu virus is higher if:

  • You work with poultry (such as farmers)
  • You travel to countries where the virus is present
  • You touch an infected bird
  • You go into a building with sick or dead birds, feces, or litter from infected birds
  • You eat raw or undercooked poultry meat, eggs, or blood from infected birds

No one has gotten avian flu virus from eating properly cooked poultry or poultry products.

Health care workers and people who live in the same house as people with bird flu may also be at higher risk of infection.

Avian flu viruses can live in the environment for long periods of time. Infection may be spread just by touching surfaces that have the virus on them. Birds who were infected with the flu can give off the virus in their feces and saliva for as long as 10 days.


Symptoms of avian flu infection in humans depend on the strain of virus.

The avian influenza virus in humans causes typical flu-like symptoms, such as:

Exams and Tests

If you think you have been exposed to the virus, call your health care provider before your visit. This will give the staff a chance to take steps to protect themselves and other patients during your office visit.

There are tests for the avian flu but they are not widely available. One type of test can give results in about 4 hours.

Your health care provider might also do the following tests:

  • Auscultation (to detect abnormal breath sounds)
  • Chest x-ray
  • Nasopharyngeal virus detection by reverse transcription-polymerase chain reaction (RT-PCR)
  • Nasopharyngeal culture
  • Throat virus detection by RT-PCR
  • White blood cell differential

Other tests may be done to look at how well your heart, kidneys, and liver are working.


Treatment varies based on your symptoms.

In general, treatment with the antiviral medication oseltamivir (Tamiflu) or zanamivir (Relenza) may make the disease less severe. You need to start taking the medicine within 48 hours after your symptoms start for it to work.

Oseltamivir may also be prescribed for persons who live in the same house people with avian flu. This may prevent them from getting the illness.

The virus that causes human avian flu is resistant to the antiviral medicines amantadine and rimantadine. These medicines should not be used in the case of an H5N1 outbreak occurs.

People with severe infection may need to be placed on a breathing machine. People infected with the virus also should be kept separate from non-infected people.

Health care providers recommend that people get an influenza (flu) shot. This may cut down the chance that the avian flu virus will mix with a human flu virus. This might create a new virus that may easily spread.

The U.S. Food and Drug Administration has approved a vaccine to protect humans from the avian flu. This vaccine could be used if the current H5N1 virus starts spreading between people. The U.S. Federal Government keeps a stockpile of H5N1 vaccine.

Outlook (Prognosis)

The outlook depends on the type of avian flu virus and how bad the infection is. The disease can be fatal.

Possible Complications

When to Contact a Medical Professional

Call your health care provider if you develop flu-like symptoms within 10 days of handling infected birds or being in an area with a known avian flu outbreak.


At this time, the U.S. Centers for Disease Control and Prevention (CDC) does not recommend against travel to countries affected by avian influenza.

The Centers for Disease Control and Prevention makes the following recommendations.

As a general precaution:

  • Avoid wild birds and watch them only from a distance.
  • Avoid touching sick birds and surfaces that may be covered in their feces.
  • Use protective clothing and special breathing masks if you work with birds or if you go into buildings with sick or dead birds, feces, or litter from infected birds.
  • If you have had contact with infected birds, watch for signs of infection. If you do become infected, tell your doctor.
  • Avoid undercooked or uncooked meat. This reduces the risk of exposure to avian flu and other foodborne diseases.

If traveling to other countries:

  • Avoid visits to live-bird markets and poultry farms.
  • Avoid preparing or eating undercooked poultry products.
  • See your doctor if you become sick after you return from your trip.

Current information regarding avian flu is available at: http://www.cdc.gov/flu/avianflu/avian-in-humans.htm.

Alternative Names

Bird flu; H5N1; H5N2; H5N8; H7N9; Avian influenza A (HPAI) H5


Centers for Disease Control and Prevention, National Center for Immunization and Respiratory Diseases (NCIRD). Avian influenza A virus infection in humans. Last reviewed: March 18, 2015. Accessed: June 3, 2015.

Levin S. Zoonoses. In: Goldman L, Schafer AI, eds.Goldman's Cecil Medicine.

Hayden FG. Influenza. In: Goldman L, Schafer AI, eds.Goldman's Cecil Medicine.

Update Date 2/4/2014

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