Key Facts about Bird Flu (H5N1) Virus

This fact sheet provides general information about bird flu and information about one type of bird flu, called avian influenza A (H5N1) that is infecting birds in Asia and has infected some humans.

What is bird flu?

Bird flu is an infection caused by influenza (flu) virus. These flu viruses occur naturally among birds. Wild birds worldwide carry the viruses in their intestines, but usually do not get sick from them. However, bird flu is very contagious among birds and can make some domesticated birds, including chickens, ducks and turkeys, very sick and kill them.


Do bird flu viruses infect humans?

The risk from bird flu is generally low to most people, because the viruses do not usually infect humans. H5N1 is one of the few bird flu viruses to infect humans, and it is the most deadly of those that have crossed the barrier.

So far, the spread of H5N1 virus from person to person has been limited and has not continued beyond one person. Nonetheless, because all influenza viruses have the ability to change, scientists are concerned that H5N1 virus one day could be able to infect humans and spread easily from one person to another.

 

How are bird flu viruses different from human flu viruses?

There are many different subtypes of type A influenza viruses. When we talk about “bird flu” viruses, we are referring to influenza A subtypes chiefly found in birds. They do not usually infect humans, even though we know they can. When we talk about “human flu viruses” we are referring to those subtypes that occur widely in humans. Influenza A viruses are constantly changing, and they can adapt over time to infect and spread among humans.

 

What are the symptoms of bird flu 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. The symptoms of bird flu may depend on which virus caused the infection.

 

How does bird flu spread?

Infected birds shed flu virus in their saliva, nasal secretions and feces. Susceptible birds become infected when they have contact with contaminated excretions or surfaces that are contaminated with excretions. It is believed that most cases of bird flu infection in humans have resulted from contact with infected poultry or contaminated surfaces. The spread of bird flu viruses from one ill person to another has been reported very rarely, and transmission has not been observed to continue beyond one person.

 

How is bird flu in humans treated?

Studies done in laboratories suggest that the prescription medicines approved for human flu viruses should work in preventing bird flu infection in humans. Flu viruses can become resistant to these drugs, so these medications may not always work. Additional studies are needed to prove the effectiveness of these medicines.

 

What is the risk to humans from bird flu?

The risk from bird flu is generally low to most people because the viruses occur mainly among birds and do not usually infect humans. However, during an outbreak of bird flu among poultry (domesticated chickens, ducks and turkeys), there is a possible risk to people who have contact with infected birds or surfaces that have been contaminated with excretions from infected birds. The current outbreak of bird influenza A (H5N1) among poultry in Asia and Europe is an example of a bird flu outbreak that has caused human infections and deaths. In such situations, people should avoid contact with infected birds or contaminated surfaces, and should be careful when handling and cooking poultry. For more information about bird influenza and food safety issues, visit the World Health Organization Web site.

 

What is a bird influenza A (H5N1) virus?

Influenza A virus – also called “H5N1 virus” – is an influenza A virus subtype that occurs mainly in birds. It was first isolated from birds (terns) in South Africa in 1961. Like all bird flu viruses, H5N1 virus circulates among birds worldwide, is very contagious among birds and can be deadly.

 

How is infection with H5N1 virus in humans treated?

The H5N1 virus currently infecting birds in Asia that has caused human illness and death is resistant to amantadine and rimantadine, two antiviral medications commonly used for influenza. Two other antiviral medications, oseltamavir and zanamavir, would probably work to treat flu caused by the H5N1 virus, but additional studies still need to be done to prove their effectiveness.

 

Is there a vaccine to protect humans from H5N1 virus?

There currently is no commercially available vaccine to protect humans against the H5N1 virus that is being seen in Asia and Europe. However, vaccine development efforts are taking place. Research studies to test a vaccine to protect humans against H5N1 virus began in April 2005, and a series of clinical trials is underway. For more information about the H5N1 vaccine development process, visit the National Institutes of Health Web site at www.nih.gov.

 

What is the risk to people in the United States from the H5N1 bird flu outbreak in Asia and Europe?

The current risk to Americans from the H5N1 bird flu outbreak in Asia is low. The strain of H5N1 virus found in Asia and Europe has not been found in the United States. There have been no human cases of H5N1 flu in the United States. It is possible that travelers returning from affected countries in Asia could be infected if they were exposed to the virus. Since February 2004, medical and public health personnel have been watching closely to find any such cases.

 

What does the CDC and California Department of Public Health (CDPH) recommend regarding the H5N1 bird flu outbreak?

In February 2004, CDC provided U.S. health departments with recommendations for enhanced surveillance and detection in the U.S. of bird influenza A (H5N1). State and local governments are developing, improving, and testing their plans for pandemic influenza. The U.S. Department of Health and Human Services, and other federal agencies are providing funding, advice, and other support. The CDC currently advises that travelers to countries with known outbreaks of 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. For more information on travel recommendations, visit the Travelers’ Health section of the CDC Web site.

 

What is the federal government doing to prepare for bird flu?
The Federal Government has a website dedicated to pandemic flu information: www.pandemicflu.gov.