It has arrived much later this winter, but experts say the swine flu is now on Australia's doorstep.
Transmission of the H1N1 virus has been elevated in New Zealand for several weeks, The Influenza Specialist Group (ISG) reports, and a jump in new infections was also now emerging in Australia.
"The timing of the flu season can vary somewhat each year," said ISG chairman Dr Alan Hampson.
"Current data now show that infections are on the increase in Australia and influenza is now at significant levels in New Zealand, which usually shortly precedes Australia.
To us this means that outbreaks are imminent."
The latest Flutracking data for NSW, issued earlier this month, points to "influenza-like illness" infections among the state's unvaccinated population rising to above four per cent.
The "sustained rise is consistent with broadening influenza activity in the community", it warned.
A Department of Health and Ageing Influenza Surveillance Report for the week ending August 13 also notes a jump in laboratory confirmed influenza cases in Victoria, South Australia and Queensland.
There have also been four pandemic influenza related deaths in 2010 reported to the National Notifiable Diseases Surveillance System.
Dr Hampson said vaccination remained the best protection against the virus which was known to pose added risks to pregnant women and younger Australians as well as Aboriginal or Torres Strait Islander people - and particularly those with chronic medical conditions.
He also warned influenza was currently a problem in a number of Asian countries, particularly India, and that travellers should be vaccinated before leaving Australia for Commonwealth Games in Delhi this October.
"Based on surveillance data, the timing for the Commonwealth Games in Delhi is around the usual peak time for influenza in that region," Dr Hampson said.
"This has obvious implications for the athletes, but also for other team members and spectators.
"It has been found that highly-trained athletes tend to be more susceptible to respiratory infections such as influenza."
