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Avian Flu
Avian flu or bird flu, as it's more commonly called, is frequently mentioned in the press but rarely fully explained. The following provides background information about avian flu, the viruses, and the risk to human health.
Do bird flu viruses infect humans?
How do people become infected with bird flu viruses?
How are bird flu viruses different from human flu viruses?
What are the symptoms of bird flu in humans?
How is bird flu in humans treated?
What is the risk to humans from bird flu?
Bird flu is a highly contagious infection caused by avian influenza viruses. 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 can cause serious illnesses and even fatalities in some domesticated birds, such as chickens, ducks, and turkeys.
Do bird flu viruses infect humans?
Usually, avian flu 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.
How do people become infected with bird flu viruses?
Most cases of avian (bird) influenza infection in humans have resulted from direct or close contact with infected poultry or surfaces contaminated with secretions and excretions from infected birds. The spread of avian influenza viruses from an ill person to another 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.
How are bird flu viruses different from human flu viruses?
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. It is likely that some genetic parts of current human influenza A viruses came from birds originally. Influenza A viruses are constantly changing, and they might adapt over time to infect and spread among humans.
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.
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.
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 avian influenza 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?
The H5N1 virus that has caused human illness and death in Asia, Europe, the Near East, and Africa is resistant to amantadine and rimantadine, two antiviral medications commonly used for influenza. Two other antiviral medications, oseltamavir (Tamiflu) and zanamavir, would probably work to treat influenza caused by H5N1 virus, but additional studies still need to be done to demonstrate their effectiveness.
What is the risk to humans from bird flu?
The highly pathogenic avian influenza A (H5N1) epizootic (animal outbreak) in Asia, Europe, the Near East, and Africa is not expected to diminish significantly in the short term. It is likely that H5N1 virus infections among domestic poultry have become endemic in certain areas and that sporadic human infections resulting from direct contact with infected poultry and/or wild birds will continue to occur. So far, the spread of H5N1 virus from person-to-person has been very rare, limited, and unsustained. However, bird flu continues to pose an important public health threat.
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