Health Encyclopedia

Avian influenza

Definition

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.

Alternative Names

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

Causes

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 one 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.

The Centers for Disease Control and Prevention reports 21 states with avian flu in birds and no infections in humans as of August 2015.

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 for 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 for 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 shed the virus in their feces and saliva for as long as 10 days.

Symptoms

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:

Cough
Diarrhea
Trouble breathing
Fever greater than 100.4°F (38°C)
Headache
General ill feeling (malaise)
Muscle aches
Runny nose
Sore throat

Exams and Tests

If you think you have been exposed to the virus, call your health care provider before your office visit. This will give the staff a chance to take steps to protect themselves and other people 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 provider might also do the following tests:

Listening to the lungs (to detect abnormal breath sounds)
Chest x-ray
Culture from the nose or throat
A method or technique to detect the virus, called RT-PCR
White blood cell count

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

Treatment

Treatment varies, and is based on your symptoms.

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

Oseltamivir may also be prescribed for people 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.

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.

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.

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

Complications may include:

When to Contact a Medical Professional

Contact your 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.

Prevention

There is an approved vaccine to protect humans from the H5N1avian flu virus. This vaccine could be used if the current H5N1 virus starts spreading among people. The US government keeps a stockpile of vaccine.

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

The CDC 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 provider.
Avoid undercooked or uncooked meat. This reduces the risk for 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 provider if you become sick after you return from your trip.

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

References

Centers for Disease Control and Prevention website. Avian influenza A virus infections in humans. www.cdc.gov/flu/avianflu/avian-in-humans.htm. Updated April 18, 2017. Accessed February 10, 2022.

Dumler JS, Reller ME. Zoonoses. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 312.

Ison MG, Hayden FG. Influenza. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 340.

Treanor JJ. Influenza viruses, including avian influenza and swine influenza. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 165.

Review Date:11/23/2021
Reviewed By:Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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