What
is avian influenza ?Avian influenza (commonly known as bird flu) is a
virus infectionwhich occurs naturally in birds. Wild birds can carry the virus
intestinally, without being affected. Avian influenza can be highly contagious
among birds, and can be rapidly fatal to many, including chickens, ducks, and
turkeys. 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,
but the highly pathogenic form spreads rapidly through flocks of poultry; the
disease has a mortality rate that can reach 100%. Where
is avian influenza usually found?The virus originated in Eastern Asia,
and has tended to spread westward; new strains appear periodically, some classified
as low pathogenicity avian influenza (LPAI), causing little harm to infected birds.
Other strains are high pathogenicity avian influenza (HPAI); causing serious illness
and death among infected birds, and similarly in people. H5N1 is currently the
HPAI causing major concern; first isolated in the east, it reached Scotland in
April 2006. How common is avian influenza ?Like
human influenza, the avian form can reach epidemic form among birds, and the disease
is endemic to the world's bird population. Low pathogenicity forms are more common
than high, and the disease accounts for many laying birds being 'off color' with
lower laying rates. How is avian influenza transmitted?Infected
birds spread the 'bird flu' virus via saliva, nasal secretions, and feces. Susceptible
birds become infected when they have contact with contaminated secretions or excretions
or surfaces contaminated by infected birds. Domesticated birds may become infected
through contact with infected waterfowl or other infected poultry, or indirectly
by contact with contaminated items. The disease is highly contagious among
birds, being spread among domestic fowl by human behaviour, as well as mingling
with wild birds; the shooting community probably have a case to answer, with millions
of young birds crossing national borders in crowded containers, before release
into the wild to spread disease in local populations before being shot for sport.
Migratory waterfowl are currently thought to be the key carriers of the
severe strains of the disease. Can avian influenza
be spread from person-to-person?The disease can be spread by infected
birds to people, through direct contact with contaminated items. There have been
no recorded cases of person-to-person spread, but viruses do alter their structures,
especially when they co-exist in the same host. It is theoretically possible that
if someone carrying a virus endemic in humans were to contract the disease, a
mutated form of the virus could develop with the ability to 'cross the species
barrier', readily infecting human beings. Pigs are susceptible to both human
and bird viruses. If a pig were infected with the bird flu virus at the same time
as a human flu virus, the animal could become a "mixing vessel", allowing
a new, form of the bird virus to arise with the ability to spread directly from
one human being to another. There is fairly strong evidence that such an
event lead to the 1918 human flu epidemic that killed upward of 20 million people. Who
is most at risk?Currently, only people who have close contact with infected
birds are considered at risk. Over three years since the problem was recognized,
about 200 human infections have been confirmed, and about 100 people have died,
worldwide; mostly in cultures where people and domestic fowls live in very close
proximity. What are the symptoms of avian influenza
?In birds, avian influenza can range from symptom-free, to ruffled feathers
and general malaise, to rapid onset of breathing difficulties and death within
two days. In human beings, mild forms of avian influenza appear to be similar
to typical human influenza, including fever, cough, sore throat, and muscle aches.
More aggressive forms have included eye infections, pneumonia, severe respiratory
distress and other life-threatening complications. The symptoms may depend on
the virus strain involved. How is avian influenza
diagnosed?Initial diagnosis may depend on the individual history, particularly
recent travel and contact with birds or avian wastes. Confirmation will depend
on laboratory tests of nose and throat swabs, plus sputum, and possibly blood
tests. Is there a treatment for avian influenza
?The H5N1 'bird flu' virus that has caused human illness and death in
Asia has become resistant to amantadine, an antiviral medication used for human
influenza. However, oseltamavir (Tamiflu) and zanamavir (Relenza), may well be
effective against the H5N1 virus, though further research is needed. Is
there a way to prevent infection?'Bird flu' is still only a small risk
to those who work with birds, their excreta, and untreated products (eg feathers).
Appropriate protective gear; including gloves, and - in some cases - masks and
goggles - couple with an educative approach, will usually be sufficient. For the
general public, a health education campaign that highlights the dangers of close
contact (eg feeding pigeons and ducks), and contact with dead animals, will be
required. Outside of affected areas, that will probably be sufficient. Where
the risk is higher - where the H5N1 virus has been identified - much tighter measures
will be required, specific to the local culture and assessed risks. These measures
will include clear directions on risky behaviour, and rigid control of bird movement
and care. What is the mortality rate for avian
influenza ?Among birds, some strains of the disease have a mortality rate
approaching 100%; death usually occurring within 48 hours of infection.
| | 2003 |
2004 | 2005 |
Total | |
Cases | Deaths |
Cases | Deaths |
Cases | Deaths |
Cases | Deaths |
| Cambodia | 0 |
0 | 0 |
0 | 4 |
4 | 4 |
4 | | China |
0 | 0 |
0 | 0 |
8 | 5 |
8 | 5 |
| Indonesia | 0 |
0 | 0 |
0 | 17 |
11 | 17 |
11 | | Thailand |
0 | 0 |
17 | 12 |
5 | 2 |
22 | 14 |
| Vietnam | 3 |
3 | 29 |
20 | 61 |
19 | 93 |
42 | | Total |
3 | 3 |
46 | 32 |
95 | 41 |
144 | 76 |
| Country | January
to March 2006 | These tables show Confirmed Human
Cases of Avian Influenza A (H5N1) Reported to WHO | |
Cases | Deaths |
| Azerbaijan | 7 |
5 | | Cambodia | 1 |
1 | | China | 8 |
6 | | Egypt | 4 |
2 | | Indonesia |
13 | 12 |
| Iraq | 2 |
2 | | Turkey | 12 |
4 | | Total |
47 | 32 |
Is there an avian influenza vaccine?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 way.
For more information about H5N1 vaccine development process, visit the National
Institutes of Health website. Can avian influenza
be controlled environmentally?While the disease is restricted to birds,
with no confirmed human-to-human transmission, there is good reason to believe
that environmental measures can contain the disease, and reduce the riskd to human
beings from infected birds. Measures vary from country to country, and include
the following: Restrictions on keeping poultry outdoor in areas of particular
risk of avian influenza. This should ensure that wild birds have no contact with
feed and water destined for poultry. There is an EU-wide ban on the collection
of birds on markets, shows, exhibitions and cultural events, unless specifically
authorised on the basis of a positive risk assessment. Birds kept in zoos
may be subject to vaccination. All vaccinated birds must be identified and recorded,
and trade in these birds will be prohibited except under specific authorisation.
Import restrictions of live birds (pets or poultry and unprocessed feathers)
where there has been confirmation of an outbreak of H5N1 avian influenza. Occupational
health guidance to protect people working with infected birds has been prepared
by a number of countries . Surveillance measures to ensure early identification
of the infection and biosecurity measures at poultry farms have been tightened
up. Experts are working on the available information on migratory bird
species, in order to assist in early warning and risk assessment Imports
controls at national borders are being stepped up, with special measures to prevent
illegal introduction of live birds and poultry products that might pose a risk
for AI virus introduction. Outdoor activities that bring people into contact
with wild birds, such as hunting and ornithology, may need to be restricted where
local outbreaks demonstrate a risk. Normal hygiene measures after handling
dead birds should be followed (hand washing, safe food preparation etc). Any
mass change in the behaviour of wild birds must be reported, to assist in identifying
diseased birds. Any abnormal mortality of wild birds must also be reported. People
collecting such dead birds must be given appropriate training in hand hygiene
after the contact with them, use of gloves, masks, cleaning and disinfection. In
the event the disease is confirmed or suspected in an area, activities such as
bird hunting must be re-assessed and appropriate action taken. Additional
measures will probably added to this list as loopholes are found and exploited
by hunters and others, risking the health of the whole community. Is
there legal protection for workers and others? All workers who may have
contact with wild birds, or domestic birds that have had contact with wild birds,
are entitled to full training and education; sufficient for them to assess the
risks to themselves, and for them to be able to work in a way that minimises or
removes the risks to the community. Failure to provide full education and sufficient
protective gear, including gloves, masks, eye shields, general protective clothing
(as appropriate to the job) and handwashing facilities, would almost certainly
be seen by the courts as negligence, particularly if this led to confirmed disease
spread. Bibliography and Further Information
Sources I regret I cannot assist with individual cases or essays and school projects,
but if it's something I've missed, I'll be happy to try and help.
Article written by Andrew Heenan BA (Hons), RGN, RMN
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