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Q&A: Bird flu
The
spread of bird flu - also known as avian flu - which has led to
human deaths in South East Asia, is causing concern.
But what is the disease and what are the possible risks to
humans?
Q: What is
bird flu?
Like humans and
other species, birds are susceptible to flu.
There are 15
types of bird, or avian, flu.
The most
contagious strains, which are usually fatal in birds, are H5 and
H7.
The type
currently causing concern is the deadly strain H5N1.
Even within the
H5N1 type, variations are seen, and slightly different forms are
being seen in the different countries affected in this outbreak.
Migratory
wildfowl, notably wild ducks, are natural carriers of the
viruses, but are unlikely to actually develop an infection.
Domestic birds
are particularly susceptible in epidemics.
This is why the
confirmation of H5N1 in birds in Turkey and Romania is causing
concern.
Pakistan has seen
cases of the H7 and H9 strains of bird flu in poultry, but no
cases of these strains have been passed to humans
Q: Is it
possible to stop bird flu coming into a country?
The fear, after
the Turkish and Romanian findings, is that H5N1 will spread
across Europe.
Because it is
carried by birds, there is no way of preventing its spread.
But that does not
mean it will be passed to domestic flocks. Experts say proper
poultry controls - such as preventing wild birds getting in to
poultry houses - which are present in the UK, should prevent
that happening.
In addition, they
say monitoring of the migratory patterns of wild birds should
provide early alerts of the arrival of infected flocks - meaning
they could be targeted on arrival.
Q: How do
humans catch bird flu?
Bird flu was
thought only to infect birds until the first human cases were
seen in Hong Kong in 1997.
Humans catch the
disease through close contact with live infected birds.
Birds excrete the
virus in their faeces, which dry and become pulverised, and are
then inhaled.
Symptoms are
similar to other types of flu - fever, malaise, sore throats and
coughs. People can also develop conjunctivitis.
Researchers are
now concerned because scientists studying a case in Vietnam
found the virus can affect all parts of the body, not just the
lungs.
This could mean
that many illnesses, and even deaths, thought to have been
caused by something else, may have been due to the bird flu
virus.
Q: How many
people have been affected?
As of 20 October,
2005, there had been 118 confirmed cases of avian flu in humans
in Indonesia, Vietnam, Thailand and Cambodia, leading to 61
deaths.
Click here to
find the latest information from the WHO on the numbers infected
and killed by avian flu.
In comparison, Sars has killed around 800 people worldwide and
infected at least 8,400 since it first emerged in November 2002.
Q: Can avian
flu be passed from person to person?
There are
indications that it can, although so far not in the form which
could fuel a pandemic.
A case in
Thailand indicated the probable transmission of the virus from a
girl who had the disease to her mother, who also died.
The girl's aunt,
who was also infected, survived the virus.
UK virology
expert Professor John Oxford said these cases indicated the
basic virus could be passed between humans, and predicted
similar small clusters of cases would be seen again.
It is not the
only instance where it has been thought bird flu has been passed
between humans.
In 2004, two
sisters died in Vietnam after possibly contracting bird flu from
their brother who had died from an unidentified respiratory
illness.
In a similar case
in Hong Kong in 1997, a doctor possibly caught the disease from
a patient with the H5N1 virus - but it was never conclusively
proved.
Q: Does this
mean there is likely to be a large outbreak of bird flu?
Experts are
concerned that this could happen. But in the Thai case, the
virus was only passed to close relatives and spread no further.
In addition, it
had not combined with a form of human flu.
This is the real
fear. Experts believe the virus could exchange genes with a
human flu virus if a person was simultaneously infected with
both.
The more this
double infection happens, the higher the chance a new virus
could be created and be passed from person to person, they say.
Concern has also
been raised by research which showed that the virus which caused
the 1918 pandemic was an avian flu virus.
Q: What would
be the consequence if this did happen?
Once the virus
gained the ability to pass easily between humans the results
could be catastrophic.
Worldwide,
experts predict anything between two million and 50 million
deaths.
Q: Is there a
vaccine?
There is not yet
a definitive vaccine, but prototypes which offer protection
against the H5N1 strain are being produced.
But antiviral
drugs, such as Tamiflu which are already available and being
stockpiled by countries such as the UK, may help limit symptoms
and reduce the chances the disease will spread.
Concerns have
been prompted by news a Vietnamese patient has become partially
resistant to the Tamiflu, drug experts plan to use to tackle a
human bird flu outbreak.
Scientists say it
may be helpful to have stocks of other drugs from the same
family such as Relenza (zanamivir).
Q: Can I
continue to eat chicken?
Yes. Experts say
avian flu is not a food-borne virus, so eating chicken is safe.
The only people
thought to be at risk are those involved in the slaughter and
preparation of meat that may be infected.
However, the
World Health Organisation recommends, to be absolutely safe all
meat should be cooked to a temperature of at least 70C. Eggs
should also be thoroughly cooked.
Professor Hugh
Pennington of Aberdeen University underlined the negligible risk
to consumers: "The virus is carried in the chicken's gut.
"A person would
have to dry out the chicken meat and would have to sniff the
carcass to be at any risk. But even then, it would be very hard
to become infected."
Q: What is
being done to contain the virus in the countries affected?
Millions of birds
have been culled in an attempt to stop the spread of the disease
among birds, which would in turn stop it being passed on to
humans.
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