SYDNEY - A YOUNG woman with underlying health problems on Saturday became Australia's fifth H1N1 flu-related death, authorities said.

The 26-year-old, from the west coast city of Perth, died late on Friday in intensive care, where she was being treated for a serious medical condition, said Western Australia's chief health officer Tarun Weeramanthri.

'We know that people with existing medical conditions are more vulnerable to the serious effects of the disease,' he said.

All five people who have died in Australia after contracting H1N1 flu were suffering from underlying conditions, and authorities have been careful not to attribute their deaths directly to the A(H1N1) virus.

Two children are currently in intensive care with the disease, including a five-year-old girl with no other health problems, authorities said. Total cases stood at 3,519 Saturday.

Meanwhile, a group of 15 Victoria state high school students on a study trip to China were quarantined in a Shanghai hotel amid fears they were infected.

The school's principal, Jill Healey, said a passenger on board their flight had been diagnosed with the virus and they had been isolated as a precaution.

'The students are in good spirits but disappointed not to be able to continue their tour of China,' Ms Healey said. None had yet shown any flu-like symptoms, she added. -- AFP