More than 2,000 cruise ship passengers have been asked to quarantine themselves for a week after two Australian children aboard the liner tested positive for swine flu.
"We are all requesting that all people onboard this ship remain in quarantine for seven days," New South Wales chief health officer Kerry Chant told reporters after the Pacific Dawn arrived in Sydney.
Two five-year-old children who arrived in Sydney onboard the ship on Monday after a South Pacific cruise tested positive for the A(H1N1) virus, bringing Australia's total of reported cases to 23.
Passengers were asked to remain in their homes or hotels.
The ship's departure for its next cruise, with a fresh contingent of guests, was delayed until health authorities gave it the go ahead, with passengers saying they would rather be inconvenienced than exposed to the flu.
"We'd be complaining if we all got sick, and the recycling air conditioning doesn't help flu and all the rest of it," one passenger told the Australian Broadcasting Corporation.
A spokeswoman for Carnival Australia, owners of the Pacific Dawn, said the ship sailed on Monday night after receiving the all-clear from New South Wales health officials.
"I think it's important to note here that we have very well-trained doctors and very well-equipped medical centres on board our ships," she said.
"In some cases we're better equipped to deal with the spread of contagious disease, better than perhaps many other holiday destinations are."
Australia's Health Minister Nicola Roxon said the number of confirmed swine flu cases in the country had risen to 23 and five schools had been closed to prevent its spread.
"We are moving into a different phase here in Australia; the disease will be spreading quickly," she told a news conference.