Swine flu - influenza A (H1N1)
What is swine flu?
Swine influenza, known as swine flu or influenza A (H1N1), is a respiratory disease of pigs caused by type A influenza viruses, most commonly the H1N1 subtype. Regular outbreaks of swine flu occur in pigs year round, and cases have been transmitted to humans. Previously, human-to-human transmission of swine influenza has been limited.
| How do new swine flu viruses arise? |
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| Pigs can be hosts for several different flu viruses – swine influenza, avian (bird) influenza and human influenza. Sometimes more than one type of influenza virus can be present in a pig at the same time and this can allow genetic material from different virus types to mix, creating a new flu virus. Pigs have been known to be a potential source of new human flu viruses for a long time. The current April 2009 outbreak of swine flu in Mexico is caused by a new virus which has a mix of genes from human, avian and swine influenza viruses. These emerging new types of influenza virus make it difficult to create useful vaccines against them. |
What is special about the current swine flu outbreak?
This April 2009 outbreak of swine influenza is of the H1N1 subtype and it has been shown to be transmitted between humans. The subtype of an influenza A virus (e.g. H1N1) is determined by the form of the haemagglutinin protein (e.g. H1) and the form of the neuraminidase protein (e.g. N1, N5) the virus carries.
Authorities fear that this H1N1 subtype has features that may allow it to be easily passed from human to human and to cause a pandemic. The outbreak has already caused many deaths in Mexico. Because the virus is so new, people do not have any immunity to it. Normally, flu viruses share some common features with the flu viruses of previous years – and so people may have a degree of resistance to them. But this new virus is different from those going before it, and so health authorities fear that people do not have any resistance to it – which gives it the potential to cause widespread infection.
| What is a pandemic? |
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| A pandemic is an epidemic of disease that affects a wide geographic area. A famous pandemic was the Spanish flu pandemic of 1918. This was also caused by an influenza virus subtype H1N1, which spread to many parts of the world infecting an estimated half the world’s population at the time, and killing millions of people. |
What are the symptoms of swine flu?
The symptoms of swine flu are very similar to those of the human flu that we are familiar with each winter. These swine flu symptoms include: fever; cough; body aches and pains; fatigue; chills; headache; runny nose; sore throat; and respiratory distress (trouble breathing). Some people have reported diarrhoea and vomiting in association with swine flu.
| Commonwealth Health Hotline for Swine influenza |
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| If you are suffering flu-like symptoms and have returned from travel, or if you are concerned about swine influenza, ring the Commonwealth’s national health hotline for information. Telephone: 1802007 |
What should I do if I think I have swine flu or have been in contact with someone who has swine flu?
If you have returned from the USA, Canada or Mexico in the last 7 days and are feeling unwell with any flu-like symptoms, call a doctor or go to your local hospital emergency department and tell them you have flu symptoms and have recently returned from overseas. Alternatively, see your local State or Territory’s Department of Health website for advice.
Are there any treatments for swine flu?
There are antiviral medicines which are used to treat influenza. Two of these are available in Australia as Relenza (zanamivir) and Tamiflu (oseltamivir). They are available only on prescription from a doctor. Health authorities have recommended these 2 antivirals for use in swine influenza outbreaks. It is possible, however, as the outbreak progresses that the virus may mutate and become resistant to these antiviral drugs.
Using antiviral medications, soon after a person is infected with flu viruses (ideally within 2 days), can inhibit the flu viruses from multiplying in a person’s body and so make the illness less severe and make the person less likely to develop serious complications.
Is there a swine flu vaccine?
There is no swine influenza vaccine at time of writing. The Australian Department of Health and Ageing doubts that this year’s influenza vaccine will give resistance to this new virus, but recommends that people still continue to receive their flu vaccination as it should help to protect them from human influenza.
What is Australia doing in response to the threatened pandemic?
The Australian Government has declared swine influenza a quarantinable disease. This gives it the power to take action and prevent the spread of the disease. Australia has strengthened its border surveillance and is focussed on limiting any spread of the virus within Australia as it occurs.
Last Reviewed: 06 May 2009
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