SYDNEY - MORE than 2,000 cruise ship passengers have been asked to quarantine themselves for a week after eight passengers and a crew member 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 ended its South Pacific cruise in Sydney.

Two five-year-old boys who arrived in Sydney onboard the ship on Monday tested positive for the A(H1N1) virus, with an adult passenger and crew member also diagnosed on Tuesday in Sydney.

Another five people from the ship returned positive test results in the neighbouring state of Queensland.

Passengers were asked to remain in their homes or hotels.

Health Minister Nicola Roxon said 175 people on board the ship had shown signs of respiratory illness and 130 were still suffering symptoms. They had been tested and offered anti-viral drugs.

The ship's departure for its next cruise to the Great Barrier Reef, 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.

A spokesman 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.

Several schools were closed late on Tuesday as the number of confirmed cases reached 45. They included four people who arrived in Sydney on a flight from Los Angeles on Sunday.

She agreed home quarantine was a voluntary measure which was impossible to police, but said there had been widespread community cooperation to date. -- AFP