Common Diseases > Avian Influenza or Bird Flu
Avian influenza or bird flu 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.
Infected birds shed influenza virus in their saliva, nasal secretions, and
faeces. Susceptible birds become infected when they have contact with
contaminated secretions or excretions or with surfaces that are contaminated
with secretions or excretions from infected birds. Domesticated birds may become
infected with avian influenza virus through direct contact with infected
waterfowl or other infected poultry, or through contact with surfaces (such as
dirt or cages) or materials (such as water or feed) that have been contaminated
with the virus.
Infection with avian influenza viruses in domestic poultry causes two main forms
of disease that are distinguished by low and high extremes of virulence. The
low pathogenic form may go undetected and usually causes only mild symptoms
(such as ruffled feathers and a drop in egg production). However, the highly
pathogenic form spreads more rapidly through flocks of poultry. This form may
cause disease that affects multiple internal organs and has a mortality rate
that can reach 90-100% often within 48 hours.
Human infection with avian influenza viruses
There are many different subtypes of type A influenza viruses. These subtypes
differ because of changes in certain proteins on the surface of the influenza A
virus (hem agglutinin [HA] and neuraminidase [NA] proteins). There are 16 known
HA subtypes and 9 known NA subtypes of influenza A viruses. Many different
combinations of HA and NA proteins are possible. Each combination represents a
different subtype. All known subtypes of influenza A viruses can be found in
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 transmission has not been observed to continue beyond one person.
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.
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.
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.
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.
While additional studies are needed to demonstrate the effectiveness of these
medicines you can do a lot to prepare with the
Bird Flu Preparedness Planner by Grattan Woodson. If an infection occurs,
Homeopathic Treatment is available and if you want to understand all the
hype, David J. Kennedy's book
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Avian influenza A (H5N1) in Asia and Europe
Influenza A (H5N1) virus also called H5N1 virus is an influenza A virus
subtype that occurs mainly in birds, is highly contagious among birds, and can
be deadly to them.
Outbreaks of avian influenza H5N1 occurred among poultry in eight countries in
Asia (Cambodia, China, Indonesia, Japan, Laos, South Korea, Thailand, and
Vietnam) during late 2003 and early 2004. At that time, more than 100 million
birds in the affected countries either died from the disease or were killed in
order to try to control the outbreaks. By March 2004, the outbreak was reported
to be under control. Since late June 2004, however, new outbreaks of influenza
H5N1 among poultry were reported by several countries in Asia (Cambodia, China
[Tibet], Indonesia, Kazakhstan, Malaysia, Mongolia, Russia [Siberia], Thailand,
and Vietnam). It is believed that these outbreaks are ongoing. Influenza H5N1
infection also has been reported among poultry in Turkey Romania, and Ukraine.
Outbreaks of influenza H5N1 have been reported among wild migratory birds in
China, Croatia, Hong Kong (SARPRC), Mongolia, and Romania.
As of January 7, 2006, human cases of influenza A (H5N1) infection have been
reported in Cambodia, China, Indonesia, Thailand, Vietnam, and most recently,
Turkey. These samples are undergoing further analysis to determine whether they
contain the H5N1 strain. For the most current information about avian influenza
and cumulative case numbers, see the World Health Organization (WHO) website at
Human health risks during the H5N1 outbreak
H5N1 virus does not usually infect people, but about 160 human cases have been
reported by the World Health Organization since January 2004. Most of these
cases have occurred as a result of people having direct or close contact with
infected poultry or contaminated surfaces. So far, the spread of H5N1 virus from
person-to-person has been rare and has not continued beyond one person.
Of the few avian influenza viruses that have crossed the species barrier to
infect humans, H5N1 has caused the largest number of detected cases of severe
disease and death in humans. In the current outbreaks in Asia and Europe more
than half of those infected with the virus have died. Most cases have occurred
in previously healthy children and young adults. However, it is possible that
the only cases currently being reported are those in the most severely ill
people, and that the full range of illness caused by the H5N1 virus has not yet
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. Because
these viruses do not commonly infect humans, there is little or no immune
protection against them in the human population. If H5N1 virus were to gain the
capacity to spread easily from person to person, an influenza pandemic
(worldwide outbreak of disease) could begin. For more information about
influenza pandemics, see
No one can predict when a pandemic might occur. However, experts from around the
world are watching the H5N1 situation in Asia and Europe very closely and are
preparing for the possibility that the virus may begin to spread more easily and
widely from person to person.
Treatment and vaccination for H5N1 virus in humans
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, oseltamavir and zanamavir, would
probably work to treat influenza caused by H5N1 virus, but additional studies
still need to be done to demonstrate their effectiveness.
There currently is no commercially available vaccine to protect humans against
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 under
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