College of American Pathologists
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  Avian Influenza (Bird Flu)




Updated July 30, 2009

What is avian influenza (bird flu)?
Avian influenza is an infection caused by avian (bird) influenza (flu) virus (H5N1).  These flu viruses occur naturally among birds.  Wild birds worldwide carry 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.

Does the avian influenza virus infect humans?
The avian influenza, or H5N1 virus, does not usually infect humans, and when it does, it has coincided with large bird flu outbreaks in poultry.

When was the first human case of bird flu documented?
In 1977, the first case of the virus spreading from a bird to a human was seen during an outbreak of bird flu in poultry in Hong Kong’s Special Administrative Region.  The virus caused severe respiratory illness in 18 people, six of whom died.  Since that time, there have been other limited cases of the H5N1 infection among humans.  Recent human cases of the H5N1 infection that have occurred in Cambodia, Thailand and Vietnam have coincided with large H5N1 outbreaks in poultry.

How do people become infected with avian influenza?
Most cases of avian influenza infection in humans have resulted from direct or close contact with infected poultry (e.g., domesticated chicken, ducks, and turkeys) or surfaces contaminated with secretions and excretions from infected birds. The spread of avian influenza viruses from person to person has been reported very rarely, and transmission has not been observed to continue beyond one person. During an outbreak of avian influenza among poultry, there is a possible risk to people who have direct or close contact with infected birds or with surfaces that have been contaminated with secretions and excretions from infected birds.

What are the symptoms of avian influenza in humans?
Symptoms of bird flu in humans have ranged from typical flu-like symptoms (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.

How is avian influenza diagnosed in humans?
A laboratory test is needed to confirm avian influenza in humans. The Food and Drug Administration approved a new laboratory test to diagnose the H5N1 virus (avain influenza) in humans.  The new “quick response” test provides preliminary results on samples from suspected H5 influenza cases within four hours once the sample arrives at a lab and testing begins.  The test has been distributed to the Laboratory Response Network (LRN) – a system of designated laboratories established to enhance early detection and surveillance activities, as well as increase laboratory response capacity associated with a potential pandemic. The test is currently available in 140 labs in all 50 states.

For more information about the avian influenza test, click on the link below to read the FDA’s press release.

Would an outbreak of avian influenza in the United States coincide with the cold and flu season?
Not necessarily. Outbreaks of pandemic flurarely occurs and do not follow the predictable seasonal patterns of cold and flu season.

How does avian influenza differ from seasonal influenza viruses that infect humans?
Unlike seasonal influenza, in which infection usually causes only mild respiratory symptoms in most people, avian influenza may follow an unusually aggressive clinical course, with rapid deterioration and high fatality rate. Pneumonia and multi-organ failure have been common among people who have become ill avian influenza.

Does the current seasonal influenza vaccine protect people from avian influenza?
No. The influenza vaccine does not provide protection against avian influenza.

Is there a vaccine to protect people from avian influenza?
Currently, there is no commercially available vaccine to protect humans against the avian influenza. However, vaccine development efforts are taking place. Research studies to test a vaccine to protect humans against avian influenza are ongoing, and a series of clinical trials are underway.

How is avian influenza in humans treated?
Most avian influenza (H5N1) viruses that have caused human illness and death appear to be resistant to amantadine (Symmetrel®) and rimantadine (Flumadine®), two antiviral medications commonly used for treatment of patients with influenza. Two other antiviral medications, oseltamivir (Tamiflu®) and zanamavir (Relenza®), might be used to treat influenza caused by the H5N1 virus, but additional studies are needed to demonstrate their current and ongoing effectiveness.

How can I reduce my risk of exposure to avian influenza?
To reduce your risk of becoming infected with any type of influenza, it is important to practice good hygiene, including:

  • Wash your hands frequently.
  • Avoid close contact with people who are sick.
  • Stay home when you are sick.
  • Cover your mouth when you cough and sneeze into your elbow.

Should I wear a surgical mask to prevent exposure to avian influenza?
Currently, wearing a mask is not recommended for preventing influenza exposure.  In the United States, disposable surgical and procedure masks have been widely used in health-care settings to prevent exposure to respiratory infections, but the masks have not been used commonly in community settings, such as schools, businesses and public gatherings.

Do I need to take any special precautions when traveling abroad?
The Centers for Disease Control and Prevention (CDC) currently advises that travelers to countries with known outbreaks of the avian influenza A (H5N1) 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. The CDC does not recommend any travel restrictions to affected countries at this time.

Is there a risk for becoming infected with avian influenza by eating poultry?
There is no evidence that properly cooked poultry or eggs can be a source of infection for avian influenza. The U.S. government carefully controls domestic and imported food products, and in 2004 issued a ban on importation of poultry from countries affected by avian influenza. The ban still is in place.

Where can I find more information on avian influenza?
To find more information on avian influenza, visit the CDC and WHO Web sites.

CDC - Avian influenza (bird flu) virus

WHO - Avian influenza