(Bird Flu, H5N1 Infection)
by Rosalyn Carson-DeWitt, MD
Avian influenza is a strain of influenza virus that primarily infects birds. It is often called the bird flu.
In Asia and Africa, there have been cases of avian influenza that have the ability to infect humans. The most significant of these avian influenza strains is called H5N1. This strain can cause serious illness and death.
Avian influenza is caused by a specific influenza type A virus. The virus is common among wild and domestic birds, but rarely infects humans. Occasionally, the virus can mutate which allows it to infect humans.
The virus is passed through contact with an infected bird's:
Avian influenza is not contracted through eating well-cooked poultry or eggs. The virus rarely passes from 1 human to another. When it does, it is usually a weakened version of the virus. Infections are being monitored to see if the virus mutates in a way that allows it to easily pass between humans.
Close contact with infected poultry increases your chance of avian influenza. This may include domestic or wild ducks, geese, chickens, or turkeys.
Your chance of infection is also increased with recent travel to an area known to have avian influenza. Avian influenza outbreaks are most common in Asia, the Middle East, and northeast Africa.
Symptoms of avian influenza may include:
More severe infections can lead to pneumonia or serious organ failure.
You will be asked about your symptoms and medical history. A physical exam will be done. You will be asked if you have had close contact with infected poultry or have recently traveled to an area known to have avian influenza.
Nasal or respiratory secretions or blood can be tested for the presence of the virus.
Antiviral medications can help decrease your symptoms and the length of time you are sick. They do not cure the flu. The sooner the medication is started the more effective it can be. Ideally, the medication should be started within 48 hours of the first symptoms.
The overall risk of getting avian influenza is small. To help reduce your chances of avian influenza:
The US Food and Drug Administration has licensed a vaccine to protect against H5N1 in adults aged 18-64. It will be made available in the event of an outbreak. Vaccinations can protect the individual and may control the spread of the infection.
Centers for Disease Control and Prevention
US Department of Agriculture
Canadian Medical Association
Avian and other zoonotic influenza. World Health Organization website. Available at:
...(Click grey area to select URL)
Accessed August 14, 2017.
Avian influenza A virus infections in humans. Centers for Disease Control and Prevention (CDC) website. Available at: https://www.cdc.gov/flu/avianflu/avian-in-humans.htm. Updated April 18, 2017. Accessed August 14, 2017.
Cornelissen LA, de Vries RP, et al. A single immunization with soluble recombinant trimeric hemagglutinin protects chickens against highly pathogenic avian influenza virus H5N1. PLoS One. 2010;5(5):e10645.
Kilany WH, Arafa A, et al. Isolation of highly pathogenic avian influenza H5N1 from table eggs after vaccinal break in commercial layer flock. Avian Dis. 2010;54(3):1115-1119.
Pandemic influenza. Centers for Disease Control and Prevention website. Available at: https://www.cdc.gov/flu. Updated July 28, 2017. Accessed August 14, 2017.
Weir E, Wong T, et al. Avian influenza outbreak: Update. CMAJ. 2004(5);170:785-786.
Last reviewed September 2018 by David L. Horn, MD, FACP
Last Updated: 8/4/2020
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