Some 700 people were reported to have been affected

More than 550 guests and 150 crew were affect by the diarrhoea and sickness bug, the cruise line told ABC news.

Some travellers were helped off the Carnival Liberty in wheelchairs, while others described spending days vomiting during the trip.

"I just threw up black and I thought I had the plague," said one passenger.

Fourteen guests and five crew were still ill and were being looked after in isolation when the ship arrived, said the liner's owner, Carnival Cruise Lines, in a statement.

The company said preliminary tests had identified the cause of the outbreak as the norovirus, which causes severe gastrointestinal illness.

'Six days'

Carnival officials said the illness had struck several guests just before they boarded the liner - which can hold some 2,800 people - on 3 November in Rome.

The ship's next departure has been delayed

Passengers described being given injections and anti-diarrhoea medication in the ship's infirmary, and sent bottled water, soft drinks and rice while quarantined in their rooms.

"Basically, I got sick... and was out for six days," passenger Brian Swanson told the Associated Press news agency. "I just want to go home."

The experience on the holiday ship deteriorated even further as several crew members caught the bug.

"Our cabin steward was struck, and we didn't have anybody to clean our cabin for five days," said Pamela Stupnik of Pueblo, Colorado, who said she and her husband had suffered from the illness for two days.

Most cruise activities and excursions had continued as scheduled, however, passengers said.