- by Dr. Andreas Lambrianides
- General Surgeon, Brisbane Australia
- Avian Influenza or 'bird flu', is an infectious viral
disease that normally affects only birds. Since 2003,outbreaks of the H5N1
strain of avian influenza in poultry have occurred in countries including
Vietnam ,Thailand ,Cambodia, Indonesia, China, South Korea, Kazakhstan,
Malaysia, Mongolia, Japan and Russia. Over 100 confirmed cases of infection
in humans have been reported, with around 60 deaths.
At present H5N1 subtype of influenza A dominates the thoughts of the medical
and wider public both local and global. Lost amongst the deluge of
information is the reason why communities are rightly concerned about this
In dissecting out the reason we need to consider the past history of
pandemic influenza and the rise of H5N1 influenza since 1997.
Our thinking about influenza has always been dominated by the great
pandemics of 1957, 1968 , 1977, and most importantly of all, the 1918
pandemic. Much has been learned about the virus and the disease from the
later pandemics but the key facts about the 1918 pandemic have been illusory
until the past few weeks.
The 1918 pandemic was, the most devastating infectious disease in recorded
human history. It stands apart from the subsequent pandemics in many ways –
the scale, the epidemiology, the severity – so much so that it has always
been felt that there was something different about the influenza subtype
(H1Na) responsible. The problem was that it could never been identified in
those times. The only possible remaining sources of the virus were in the
tissues of victims and the pathology archives.
New molecular technology has allowed a reconstruction of the 1918 influenza
virus front these sources.
The 1918 influenza virus, was different from the other pandemic subtypes
,and this was the result of mixing and exchanging genetic material between
avian strains and animal strains of influenza. The 1918 influenza subtype
appears not to have intermixed but to be an avian subtype that directly
infected humans. Of even more concern is that there are close similarities
between the 1918 subtype and H5N1.
The key points are:
1) H5N1 has spread widely through the migratory wildfowl population and this
in turn has spread the virus geographically far and wide.
- The virus does not harm the
2) H5N1 has from time to time infected the domestic fowl population with
devastating consequences for the flocks. It would appear that
- the infection strain(s) of
H5N1 are becoming more pathogenic as a number of bird species that are
usually not susceptible have died.
3) H5N1 infection of humans is associated with a high mortality
4) A global population that as no immunity to this subtype nor do we have a
vaccine at present. Antiviral drugs are available but supplies
- will have to be controlled.
5) A epidemiological record indicating that we are long overdue for an
6) A highly mobile human population.
7) Sporadic outbreaks occurring in communities that have inadequate
resources to address the problem.
8) The impact that the S.A.R.S epidemic have on the community.
We now have a situation where two of the three requisites for building the
trigger for an influenza pandemic, namely the lack of immunity and an
influenza virus capable of infecting humans exist.
The last requirement:
It is the ability to be transmitted readily from person to person that is
missing from the picture.
For this to occur either a mutation in the avian H5N1 in the wild or the
development of a genetic hybrid, as a result of co-infection in a human or
animal with the avian H5N1 and on of the other human or animal influenza
viruses, needs to occur.
There is no confirmed evidence of person to person spread in the current
H5N1 avian influenza outbreak. The latest evidence about the nature of the
subtype that caused the 1918 pandemic is a concern. It points to a
mutational event in a similar avian subtype that allowed direct infection of
humans as well as human-to-human transmission.
People traveling overseas to avian influenza affected countries are
currently only at risk of contracting bird flu if they have close contact
with infected birds or raw poultry products. The virus is found in bird
faeces and respiratory secretions and does not easily spread from birds to
humans. The risk of contracting the disease from occasional contact with an
infected bird, such as when traveling on public transport, is extremely low.
Countries that import live chickens, raw chicken products or eggs, are at
risk of contracting bird flu from handling, eating poultry, or poultry
The usual symptoms of avian influenza are similar to those of other forms of
influenza, such as, high fever, cough, fatigue and aching muscles. Runny
nose and sneezing are occasionally present. Antiviral medications such as
oseltamivir (Tamiflu) and zanamivir (Relenza) can be used in the treatment
of avian influenza. Antibiotics may be required for secondary bacterial
infections such as pneumonia. Pneumonia is a very common complication of
avian influenza. Around half of the confirmed cases of avian influenza have
died, mainly from lung or other organ failure. Travelers to countries where
avian influenza is present should: avoid situations where they may come into
close contact with birds, such as poultry farms and live bird markets avoid
raw chicken, eggs, and other poultry products. If it is necessary to handle
or cook poultry and eggs, ensure that they are handled hygienically with
careful attention to hand washing after handling, and that they are
thoroughly cooked, as this destroys the virus. Wash hands regularly and more
frequently than usual.