Avian influenza (patient information)
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For patient information about the human influenza virus that is not related to bird exposure, see Human influenza
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Roseann Day; Assistant Editor(s)-in-Chief: Michael Andrew Gibson [2]
Overview
Avian influenza, commonly known as Bird Flu, is a strain of the influenza virus which infects birds. Most bird flu viruses can only infect other birds. However, bird flu can pose health risks to people. The first case of a bird flu virus infecting a person directly was in Hong Kong in 1997. Since then, the bird flu virus has spread to birds in countries in Asia, Africa and Europe.
How is Avian influenza different in animals vs. humans?
Avian influenza in birds: Avian influenza is an infection caused by avian (bird) influenza (flu) viruses. These influenza viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, avian influenza is very contagious among birds and can make some domesticated birds, including chickens, ducks, and turkeys, very sick and kill them.
Human infection with avian influenza viruses: There are many different subtypes of type A influenza viruses. Usually, “avian influenza virus” refers to influenza A viruses found chiefly in birds, but infections with these viruses can occur in humans. The risk from avian influenza is generally low to most people, because the viruses do not usually infect humans. However, confirmed cases of human infection from several subtypes of avian influenza infection have been reported since 1997. Most cases of avian influenza infection in humans have resulted from contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretion/ excretions from infected birds. The spread of avian influenza viruses from one ill person to another has been reported very rarely, and has been limited, inefficient and unsustained.
“Human influenza virus” usually refers to those subtypes that spread widely among humans. There are only three known A subtypes of influenza viruses (H1N1, H1N2, and H3N2) currently circulating among humans. Influenza A viruses are constantly changing, and they might adapt over time to infect and spread among humans.
During an outbreak of avian influenza among poultry, there is a possible risk to people who have contact with infected birds or surfaces that have been contaminated with secretions or excretions from infected birds.
What are the symptoms of Avian influenza?
Symptoms of avian influenza in humans have ranged from typical human influenza- like symptoms (e.g., fever, cough, sore throat, and muscle aches) to eye infections, pneumonia, severe respiratory diseases (such as acute respiratory distress), and other severe and life-threatening complications. The symptoms of avian influenza may depend on which virus caused the infection.
What causes Avian influenza?
The avian influenza is caused by the H5N1 virus, a subtype of type A influenza virus.
Who is at highest risk?
For current information about avian influenza A (H5N1) outbreaks, see the CDC Outbreaks page.
When to seek urgent medical care?
If there is any suspicion of avian influenza infection, it is recommended that medical care is sought immediately.
Diagnosis
If you think you have been exposed to avian influenza, call your health care provider before your visit. This will give the staff a chance to take proper precautions that will protect them and other patients during your office visit. Tests to identify the avian flu exist but are not widely available. A test for diagnosing strains of bird flu in people suspected of having the virus gives preliminary results within 4 hours. Older tests took 2 to 3 days. Your doctor might also perform the following tests:
- Auscultation (to detect abnormal breath sounds)
- Chest x-ray
- Nasopharyngeal culture
- White blood cell differential
Other tests may be done to look at the functions of your heart, kidneys, and liver.
Treatment options
Studies done in laboratories suggest that some of the prescription medicines approved in the United States for human influenza viruses should work in treating avian influenza infection in humans. However, influenza viruses can become resistant to these drugs, so these medications may not always work. The H5N1 virus that has caused human illness and death in Asia is resistant to amantadine and rimantadine, two antiviral medications commonly used for influenza. Two other antiviral medications, oseltamivir and zanamivir, would probably work to treat influenza caused by H5N1 virus, but additional studies still need to be done to demonstrate their effectiveness.
Where to find medical care for Avian influenza?
Directions to Hospitals Treating Avian influenza
What to expect (Outlook/Prognosis)?
Of the human cases associated with the ongoing H5N1 outbreaks in poultry and wild birds in Asia and parts of Europe, the Near East and Africa, more than half of those people reported infected with the virus have died. Most cases have occurred in previously healthy children and young adults and have resulted from direct or close contact with H5N1-infected poultry or H5N1-contaminated surfaces. In general, H5N1 remains a very rare disease in people. The H5N1 virus does not infect humans easily, and if a person is infected, it is very difficult for the virus to spread to another person.
Possible complications
Prevention
Prevention of avian influenza is key. Simple things can be done to avoid infection, such as:
- Safely handle produce. You cannot get avian influenza from properly handled and cooked poultry and eggs. There currently is no scientific evidence that people have been infected with bird flu by eating safely handled and properly cooked poultry or eggs.
- Masks. Currently, wearing a mask is not recommended for routine use (e.g., in public) for preventing influenza exposure.
- Travel. CDC does not recommend any travel restrictions to affected countries at this time. However, CDC currently advises that travelers to countries with known outbreaks of H5N1 influenza avoid poultry farms, contact with animals in live food markets, and any surfaces that appear to be contaminated with feces from poultry or other animals.