Passengers from Majestic Princess arrived in Sydney Harbour on Saturday morning after a 12-day cruise of New Zealand, which included docking at Port Chalmers, Dunedin.
New South Wales Health confirmed the ship was at the highest Covid-19 alert possible for those on board, with a Tier 3 warning.
That meant at least 20% of people who were on board the cruise ship had the virus.
It was estimated 800 passengers and crew were carrying the disease, of the combined 4600 on board the vessel.
University of Otago epidemiologist Professor Michael Baker described it as a "major outbreak" of Covid-19.
The ship should have taken more care to reduce infections, he said.
"I think it’s appalling. If they really have had 800 people infected at one time, they’re really not looking after the safety of their passengers."
The cruise ship industry should reflect on whether it had the proper protocols in place to care for infected passengers, Prof Baker said.
A Ministry of Health spokesman said while in New Zealand the cases on board the ship were managed by the ship’s medical team "and the situation monitored on shore by local public health staff".
The ship docked in Port Chalmers at 8am on November 4, and many passengers opted to disembark and spend the day in Dunedin before leaving about 7.30pm that evening.
Concerns were raised by members of the public at the time about the number of tourists choosing to use the public bus instead of the cruise-provided shuttles.
Mr Radich said the news of cruise passengers visiting the city carrying Covid-19 was no cause for alarm.
The measures taken by medical professionals on the front lines meant Dunedin had not faced massive outbreaks, he said.
"The health professionals have been prepared to deal with Covid for some time."
Dunedin residents were already cautious about catching the disease, but most people were "resigned" that they would catch it, he said.
"Because of the shots, the Covid vaccine is so prevalent in the community that most people cope with being unwell with it."
He believed Dunedin was prepared for cruise ships to have passengers with Covid-19.
"My main concern is about whether we can provide enough entertainment for those people on cruise ships, as opposed to Covid.
"I think we are prepared enough," he said.
Mandatory Covid-19 vaccinations and pre-departure testing are no longer required on most cruise ships.
Princess Cruise Lines’ website said once on board, any traveller who tested positive faced a five-day isolation in their cabin.
The Ministry of Health spokesman said there was a legal requirement on ships’ captains to notify the public health service throughout their New Zealand journey of any suspected infectious diseases like Covid-19 on board.
They also had to show they were "taking the necessary isolation and quarantine action", including keeping anyone who was sick or who had tested positive for Covid-19 in isolation on board. — Additional reporting The New Zealand Herald/RNZ
