Avian Influenza (Bird Flu)

What is bird flu? Bird flu is an infection caused by a certain kind of avian influenza virus. Although there are many kinds of bird flu, the most common kinds that concern health workers are H5N1 and H7N9 bird flu viruses. These viruses are found in wild birds. Most of the time, wild birds don’t get sick from the virus…

Avian Influenza (Bird Flu)

Topic Overview

What is bird flu?

Bird flu is an infection caused by a certain kind of avian influenza virus. Although there are many kinds of bird flu, the most common kinds that concern health workers are H5N1 and H7N9 bird flu viruses. These viruses are found in wild birds. Most of the time, wild birds don’t get sick from the virus. But wild birds can easily pass the virus to birds that are being raised for food, such as chickens, ducks, and turkeys. The virus can cause them to get very sick.

Usually bird flu virus is not passed from birds to people. But since 1997, some people have become sick with this serious, deadly kind of bird flu. Most of these infections have been in Asian countries among people who have had close contact with birds raised on farms.

What causes bird flu?

Bird flu is caused by a virus. After a wild bird infects a farm-raised bird, the virus can easily and quickly spread among hundreds or thousands of birds. Sick birds must then be killed to stop the virus from spreading.

People who come into contact with sick chickens, ducks, or turkeys are more likely to get the virus. Bird flu virus can be passed through bird droppings and saliva on surfaces such as cages, tractors, and other farm equipment.

Most people don’t need to worry about getting sick with bird flu virus. You cannot get bird flu from eating fully cooked chicken, turkey, or duck, because heat kills the virus.

Why are people so worried about bird flu?

In a few cases, bird flu was passed from one person to another person, not from a bird to a person. But this was very rare. The bird flu virus can make people sicker than other kinds of flu viruses. Even though only a few hundred people are known to have been sick with bird flu, more than half of them have died.

Experts also worry because the bird flu virus is so different from other flu viruses that our bodies do not have immunity against it. Not having immunity means that our bodies have a hard time fighting the virus. It also means that anyone, including those who are otherwise very healthy, can get seriously ill if he or she gets bird flu.

What are the symptoms?

At first, the symptoms of bird flu can be the same as common flu symptoms, such as:

  • A fever.
  • A cough.
  • A sore throat.
  • Muscle aches.

Sometimes bird flu also can cause other symptoms, such as:

Bird flu can quickly progress to pneumonia and acute respiratory distress syndrome, a serious lung problem that can be deadly. For the people who die from bird flu, the average length of time from the start of symptoms until death is 9 to 10 days.footnote 1

Call your doctor right away if you have traveled somewhere or live in an area where there is bird flu and you have a fever and a hard time breathing.

How is bird flu diagnosed and treated?

If your doctor thinks that you may have bird flu, he or she will do a physical exam and ask you questions about your symptoms and past health. Your doctor will also ask where you live, where you have traveled recently, and if you have been near any birds. Then your doctor may order blood tests, nasal swabs, or other tests, such as X-rays, to help find out what is making you sick.

Some questions your doctor might ask are:

  • Have you been within 3 ft (1 m) of live, sick, or dead poultry, or with wild birds?
  • Have you eaten raw or poorly cooked poultry or eggs?
  • Have you had close contact (touching or speaking distance) with someone from an area affected with a bird flu virus who has a severe respiratory illness or who later died from an unknown cause?
  • Are you a lab or poultry worker who might have been exposed to a bird flu virus?

How bird flu is treated depends on what the virus is doing to your body. In some cases, antiviral medicines may help you feel better. But experts are concerned that certain antiviral medicines may not work against bird flu.

If you have bird flu, you will stay in a private hospital room (isolation room) to reduce the chances of spreading the virus to others. When your doctors and nurses are caring for you, they will wear gloves and gowns. Some people who have bird flu may need a machine called a ventilator to help them breathe better. Other people may need a machine to help the kidneys work better (dialysis). More than half of the time, bird flu leads to death.

How can bird flu be prevented?

The World Health Organization and the U.S. Centers for Disease Control and Prevention are preparing for the possibility that bird flu could spread to people all over the world in what is called a pandemic. The U.S. Food and Drug Administration (FDA) has approved human vaccines to protect against bird flu. But immunization is not available for the public right now. The vaccines are kept in a U.S. government stockpile.footnote 2 Officials are also storing up large supplies of antiviral medicines. The U.S. government has also developed a flu plan. This is a plan to prepare for a pandemic and to make sure that as few people as possible get the virus.

International health organizations now require that all infected birds be killed. Some countries have programs to clean up poultry farms and to check that all birds are healthy before they are sold. In 2004, the United States stopped buying poultry from most Asian countries.

Even though there is a lot of talk about bird flu, most people in the United States don’t have to worry about getting it. As of January 2015, three cases of bird flu in humans had been reported in the U.S. and Canada. All of these cases were in people who got the disease while in China and then traveled to North America.

You can take steps to lower your chances of getting infected.

  • If you live in an area with bird flu, or if you are traveling to a country where there is bird flu:
    • Avoid poultry farms, poultry-processing factories or plants, and close contact with chickens, turkeys, or ducks.
    • Stay away from open-air markets where live birds are sold.
  • If you have been exposed to the virus, your doctor will watch you for signs of illness for 10 days.
  • Your doctor may give you medicine to reduce your risk for getting the disease.
  • If you are traveling to a country where there is bird flu, ask your doctor about getting a regular flu shot. It is best to do this at least 2 weeks before you leave. This will not prevent bird flu, but it may help you avoid getting the regular flu.
  • Keep your hands clean by washing them often with soap and warm water or using a hand gel that kills germs. If you use a hand gel, be sure to buy only gels made with alcohol. They do the best job of cleaning your hands.
  • Do not eat raw or poorly cooked eggs or poultry. But you can safely eat fully cooked eggs and fully cooked chicken, duck, and turkey, because heat kills the virus.

Latest information about avian influenza

These organizations are studying and keeping track of bird flu, including what is being done to prevent its spread. Their websites have the most up-to-date information about bird flu:

  • U.S. government. You can find information at www.flu.gov/about_the_flu/h5n1.
  • U.S. Centers for Disease Control and Prevention (CDC). You can find information at www.cdc.gov/flu/avianflu.
  • World Health Organization (WHO). You can find information at www.who.int/influenza/human_animal_interface/avian_influenza/en.



  1. Writing Committee of the Second World Health Organization Consultation on Clinical Aspects of Human Infection with Avian Influenza A (H5N1) Virus (2008). Update on avian influenza A (H5N1) virus infection in humans. New England Journal of Medicine, 358(3): 261–273.
  2. U.S. Food and Drug Administration (2007). FDA approves first U.S. vaccine for humans against the avian influenza virus H5N1. FDA News. Available online: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/2007/ucm108892.htm.

Other Works Consulted

  • Public Health Agency of Canada (2012). Current avian influenza (H5N1) affected areas. Available online: http://www.phac-aspc.gc.ca/h5n1/index-eng.php.
  • Schünemann HJ, et al. (2007). WHO rapid advice guidelines for pharmacological management of sporadic human infection with avian influenza A (H5N1) virus. Lancet Infectious Disease, 7(1): 21–31.
  • U.K. Department of Health (2011). Bird flu and pandemic influenza: What are the risks? Available online: http://www.dh.gov.uk/en/Aboutus/MinistersandDepartmentLeaders/ChiefMedicalOfficer/CMOtopics/DH_4102997.
  • Ungchusak K, et al. (2005). Probable person-to-person transmission of avian influenza A (H5N1). New England Journal of Medicine, 352(4): 333–340.
  • World Health Organization (2011). Fact Sheet: Avian Influenza (“Bird Flu”). Available online: http://www.who.int/mediacentre/factsheets/avian_influenza/en/index.html.
  • Writing Committee of the World Health Organization (WHO) Consultation on Human Influenza (2005). Avian influenza A (H5N1) infection in humans. New England Journal of Medicine, 353(13): 1374–1385.


Current as ofJune 9, 2019

Author: Healthwise Staff
Medical Review: Adam Husney, MD – Family Medicine
E. Gregory Thompson, MD – Internal Medicine
Leslie A. Tengelsen, PhD, DVM – Epidemiology

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