An
influenza pandemic occurs when a new strain
of influenza virus emerges, spreading around
the globe and infecting many people at once.
An influenza virus capable of causing a
pandemic is one that people have no natural
immunity to, can easily spread from person
to person, and is capable of causing severe
disease in humans.
What is bird flu and is it going to cause
a flu pandemic?
Bird flu, or avian influenza, is an infectious
disease of birds caused by type-A strains
of the influenza virus. There have been
a number of outbreaks of bird flu recently
in Asia and Europe. There have also been
some cases of people catching bird flu as
a result of close contact with sick poultry.
Because the bird flu virus has infected
a small number of people and because it
causes severe illness or death, even in
young, otherwise healthy people, it is being
closely watched in case it undergoes genetic
changes that would make it able to spread
easily from person to person.
If these changes occur, then it could cause
a pandemic. So far, this has not occurred.
Organisations such as the World Health Organisation
(WHO) and the Australian Government are
concerned that this may happen in the future.
History of Avian Influenza
The natural reservoir of avian influenza
viruses are migratory waterfowl – most
notably, wild ducks – and these birds
are also the most resistant to disease.
Domestic poultry, including chickens and
turkeys, are particularly susceptible.
Domestic flocks coming into contact with
wild migratory waterfowl have been implicated
as a frequent cause of outbreaks and live
bird markets have also played a significant
role in the spread of epidemics.
It has been noted that there are about 16
sub-types of influenza virus known to infect
birds, but to date, all outbreaks of the
highly pathogenic form have been caused
by the subtypes H5 and H7.
The most recent cause for concern occurred
in December 2003 and January 2004, when
laboratory tests confirmed the presence
of H5N1 avian influenza virus in human cases
of severe respiratory disease in Vietnam.
Since then, there have been three waves
of disease, affecting multiple countries
in Asia.
As of November 1, 77 human cases had been
reported to the WHO, of which 31 deaths
were attributed to the virus. Fortunately,
none of the avian influenza viruses have
developed the ability to spread easily from
person to person, which is a prerequisite
for a pandemic.
SQNLDR Ball is a clinical policy nurse with
Defence Health Services.
Frequently
Asked Questions
What
is an influenza (or flu) pandemic?
A flu pandemic is a worldwide outbreak of
disease that occurs when a new influenza-A
virus appears in humans, causes serious
illness and spreads easily from person to
person.
Is a flu pandemic different to the flu
that occurs every year?
The seasonal outbreaks, or epidemics, of
flu that occur each year are caused by subtypes
of influenza viruses that are already circulating
among people, so there is already a level
of immunity in the community.
Because we know which viruses are circulating
each year, we can also vaccinate people
for them. Pandemic flu is caused by an entirely
new virus sub-type, which no-one would have
immunity to. The pandemic can spread very
quickly before a vaccine becomes available,
affecting a greater number of people and
likely causing greater sickness and death
than a seasonal flu.
Is bird flu or pandemic flu in Australia?
There are no current reports of bird flu
in animals or humans in Australia. A truly
pandemic virus has not emerged yet anywhere
in the world.
What is the current level of threat of
a pandemic in the world?
A close watch is being kept on the bird
flu outbreaks. An expert group in Australia
met at the end of May this year and determined
that the threat level is Overseas-3. This
means there are some human bird flu cases
overseas, but the infection is limited and
doesn’t appear to be readily passing
from human to human. A pandemic would be
declared if we reached Overseas-6 –
that is, when there is increased and sustained
transmission of human bird flu in the general
population.
In a recent statement, the Commonwealth
Chief Medical Officer said the accepted
likelihood of an influenza pandemic in the
next one-to- two years was about 10 per
cent.
More bird flu questions answered next
edition.
