In South Korea yesterday, 23 members of an Australian lacrosse team were being held in a quarantine facility after a player tested positive for the virus.

A professor from Queensland's University of Technology emailed media outlets on Saturday to say he and a group of his students had been quarantined in Beijing for a week because of the presence of swine flu in Australia.

Professor Alan Knight, who leads the journalism program at the university, said the group had been ordered to move to a new hotel from today.

Ms Roxon said seven people were being treated in intensive care units, four in Victoria, two in South Australia and one in Tasmania. "Those who have been hospitalised generally have had other conditions or complications, such as … respiratory conditions," she said.

Greg Tannock, a virologist from the Burnet Institute in Melbourne, said although it was difficult to estimate, up to one in three people could have picked up the virus by now. "But that's based on sheer gut feeling … We need hard data," the professor said.

The president of the Australian Medical Association Victoria, Harry Hemley, said doctors had been overwhelmed with people suffering respiratory infections in recent weeks.

"I would say about one-third of the population has some sort of upper respiratory infection right now, but I can't say how many of those have swine flu," he said.

Dr Hemley said many GPs had been exposed to the virus while caring for patients because protective equipment released from the Federal Government's stockpile had not yet arrived.