Swine flu's impact on Australian hospitals is emerging, as one batch of patient data shows almost a doubling of "acute respiratory illness" cases over winter.
People in need of hospital treatment for flu-like illness in the three months to August jumped to 2,378 cases across 35 hospitals in northern NSW this year.
The figure was up from 1,267 cases last year and 1,736 cases in 2007, across the Hunter New England Area Health Service (HNEAHS).
Cases peaked in July this year, a month earlier than they did in last year's mild ordinary flu season and the severe ordinary flu season of 2007.
"Compared with 2007 and 2008, the HNEAHS experienced a rapid, early increase in hospitalisations for acute respiratory illness, coinciding with the emergence of (swine flu)," according to research published online by the Medical Journal of Australia (MJA) on Monday.
"Furthermore, a disproportionate burden of hospitalisations occurred among people aged five to 61 years ... particularly those aged 17 to 31 years."
Comparing patient data for the whole month of May - before the swine flu arrived in Australia - to the whole month of July, shows a 260 per cent increase in patients with acute respiratory problems across the hospitals.
The paper also warned that further monitoring was needed as the trend of more flu cases, more young people involved and an earlier peak, could also occur in Australia during winter next year.
In an accompanying letter published online by the MJA, Dr Patrick Charles and colleagues said the swine flu had rapidly spread to more than 160 countries since it emerged in Mexico in April.
"Confirmed laboratory infections now number over 160,000 with millions of people probably already infected and further spread inevitable," said Dr Charles, from the Department of Infectious Diseases at Melbourne's Austin Hospital.
Australians seeking their free swine flu vaccination should contact their GP.
