What is Bird Flu? Should We Be Concerned?
Medical Author: Melissa Conrad Stoppler, MD
Medical Editor: Dennis Lee, MD
Bird flu (also referred to as avian flu), as the name implies, is an infection in
birds caused by an influenza
virus. Influenza viruses that infect birds often do
not cause illness in birds. Since the viruses are highly contagious, danger to
humans arises when domesticated birds (for example chickens, ducks, and turkeys)
become infected. While bird flu usually poses no
threat to humans, instances of transmission of bird flu to humans have been
reported since 1997, and over 100 of people have been infected in the current
outbreak that began in Southeast Asia in mid-2003.
Birds infected with avian influenza virus can transmit
the virus to humans through their excretions - saliva, nasal secretions, and feces. During an
outbreak of bird flu among poultry, there is a possible risk of spread to people
who have contact with infected birds or surfaces that have been contaminated by
infected birds.
The current outbreak of bird flu that has affected
humans involves the influenza A (H5N1) virus, sometimes referred to as the "H5N1
virus". Outbreaks of influenza H5N1 infection occurred in poultry in eight
countries in Asia during late 2003 and 2004, resulting in more than 150 million
birds either dying from the disease or being killed in order to try to control
the outbreak. This
widespread outbreak also led to documented human infections and deaths in
several countries.
By March 2004, this outbreak was considered to be under control. Beginning in
late June 2004, however, new outbreaks of influenza H5N1 among poultry were
reported by several countries in Asia (Cambodia, China [Tibet ], Indonesia,
Kazakhastan, Malaysia, Mongolia, Russia [ Siberia ], Thailand, and Vietnam).
Most recently, influenza H5N1 has been reported among poultry in Turkey and
Romania. Outbreaks in wild and domestic birds are also under investigation in
other countries.
Despite efforts to contain the outbreak, the World Health Organization (WHO)
now considers the virus to be endemic in birds (meaning that the infection is
steadily maintained) in many parts of Indonesia and Viet Nam and in some parts
of China, Cambodia, and Thailand.
When Bird Flu Infects Humans
Bird flu symptoms in humans can vary and range from "typical" flu symptoms
(fever, sore throat,
muscle pain) to eye infections and pneumonia. The disease caused by the H5N1
virus is a particularly severe form of pneumonia that leads to viral pneumonia and multi-organ failure in many people who become infected.
Up to 50% of humans who contract bird flu die from the infection. During an
outbreak of bird flu, people should avoid contact with domesticated bird
populations and surfaces that may have been contaminated by bird excretions.
Over 100 humans have become infected in the current bird
flu outbreak. Confirmed cases of human infections have occurred in Cambodia,
Indonesia, Thailand, and Viet Nam. Most of those infected have come from rural
areas where many people keep poultry flocks that often roam freely and enter
dwellings. Infected birds shed virus in their feces, leading to widespread
contamination of homes and surroundings. Most of the people who have become
infected were previously healthy adults and children. Infection also occurs during the
slaughter of infected birds.
Research has suggested that the prescription antiviral
medicines approved to
treat human flu virus infections (such as Tamiflu) should work in helping
preventing bird flu infection in humans. However, 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.
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