In April 2009, a new strain of influenza, a virus called 'H1N1 2009 influenza', was identified in Mexico. Due to the speed the virus spread around the world and being a new strain of flu, the World Health Organisation declared it a pandemic in June 2009. This H1N1 influenza strain is referred to as both 'pandemic flu' and 'swine flu'.

The first case in Australia was in May 2009. By February 2010, there were more than 5000 people hospitalised and nearly 200 deaths due to pandemic flu. Reports indicate that most of those who died had underlying medical conditions, including cancer, diabetes mellitus and morbid obesity. The median age of death was 53 years, compared to the median age of death from seasonal flu from 2001 to 2006, which was 83 years.

The Federal Minister for Health and Ageing announced in a media release that as of 1 December 2010 Australia's Pandemic Phase moved from PROTECT to ALERT which signified the end of the H1N1 influenza pandemic in Australia. The Department of Health and Ageing reported that there were 44,403 confirmed cases of swine flu in Australia since May 2009, including 6767 in 2010.

The Centers for Disease Control and Prevention estimate that globally there were approximately 284,500 fatalities as a result of the pandemic, with 59 per cent of the deaths occurring in south-east Asia and Africa, and 80 per cent of the victims under 65 years of age.