Both swine flu and more common strains of flu are expected to cause a double whammy flu threat this year, health authorities warn.

New cases of swine flu are now emerging in Australia after a respite over the summer season, said Dr Alan Hampson, chair of the Influenza Specialist Group and consultant to the World Health Organization.

The H1N1 swine flu was most health-damaging in people under 65, pregnant ladies and the chronically ill, as observed by the second half of 2009.

Australia is very unlikely to avoid a return of widespread swine flu infection this winter, said Dr Hampson, and the country is likely to be joined by another flu strain.

We don't expect the flu season to be only swine influenza this year, Dr Hampson said. There is an A: Perth strain out there ... that has its greatest impact in elder people.

Swine flu, as you've seen last year, has its greatest impact on young people. We may well have a season where we've got two viruses affecting largely different groups of the population.

All Australians over 65, and those with pre-existing illness such as heart and lung disease, diabetes, and kidney problems should get themselves immunized ahead of the flu season, which officially begins in May, said Dr Hampson.

The federal government has broaden the free seasonal flu vaccine eligibility criteria, which will provide protection against the swine flu and other two flu strains expected to circulate.

Administration of the free vaccine - up to five million of them - will be given to older Australians and other high risk groups by GPs.

Free dedicated swine flu vaccine can still be accessed by Australians, by contacting their GP.

Australia Medicine