The swine flu virus is now resistant to key flu medicine Tamiflu, a new Australian study has found. This finding raises fears a new outbreak may be difficult to fight.
The research found that one in five cases of swine flu in one area in 2011 were resistant to the antiviral medicine, the Herald Sun reported.
According to Dr Aeron Hurt from the World Health Organisation collaborating centre for flu research in Melbourne, the bug appears more prone than other types of flu to developing drug resistance.
He suggested restricting access to anti-viral treatments to limit further resistance developing.
While just 2 per cent of swine flu strains around the world are resistant to Tamiflu, the Australian research found mutations in all strains of the swine flu that suggest they might be prone to develop resistance.
Tamiflu resistance develops when an individual under treatment receives the drug to control their symptoms.
In most flu viruses, the changes that make the virus resistant to treatment also make it less likely to spread to others.
With swine flu, this has not happened and the virus remains fit enough to spread to others, Dr Hurt said.
Research on patients in Newcastle NSW in 2011 found just one person in the area had used Tamiflu but the resistant form of the virus spread to 20 per cent of all those who developed swine flu in that region.
The only way to combat the growth of drug resistant strain of the virus is to save medicines for the most needy cases, Dr Hurt said.
Swine flu has not yet developed resistance to Relenza, an inhaled form of anti-viral treatment.
But Dr Hurt said most pharmacies do not stock Relenza and it is not widely used in hospitals.