A passenger on a cruise ship in Akaroa, Canterbury, is being tested for coronavirus.

Passengers on board the Golden Princess are not being allowed off the ship which arrived in Akaroa Harbour on Sunday morning.

Three passengers on board had been quarantined by the ship's doctor. One of the three had developed symptoms of Covid-19 and was being treated as a suspected case. That person would be tested on Sunday with results expected on Monday.

A spokesman for Princess Cruises, which operates the ship, said the guests involved had previously travelled on an international flight from Los Angeles on which a passenger later tested positive for Covid-19 in Australia. 

"Two guests had been referred to the ship as part of Victoria Health's normal contact inquiries in relation to the international flight. Both are well but have been isolated in their cabins as a precaution. A third guest, subsequently identified as having travelled on the flight, had reported respiratory symptoms while on board and has also been isolated pending precautionary health testing."

The ship had travelled to Akaroa from Port Chalmers, Dunedin. A spokesman for the port could not be reached for comment. 

The ship departed Melbourne, Australia, on March 10 for a 13-day New Zealand itinerary. According to the Akaroa cruise ship schedule, 2600 passengers were expected to be on board and a further 1100 crew members.

The Princess Cruises spokesman could not say if passengers disembarked in Port Chalmers or if the boat would continue on to Wellington. In a public Facebook page for the ship, some people expressed concern for elderly relatives on board.

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Canterbury District Health Board (CDHB) medical officer of health Dr Ramon Pink said the public health team was taking a precautionary approach. The three people were in quarantine, and the cruise ship company had been very cooperative.

"We realise this is disappointing news for other passengers and tourism/hospitality operators in Akaroa and Canterbury who were expecting to host the passengers today. 

"We cannot risk the potential further spread if this person tests positive.

"Two of the three people isolated have been in contact with a confirmed case in the past 14 days," Pink said. 

Prime Minister Jacinda Ardern announced on Saturday from midnight on Sunday, everyone arriving in New Zealand will have to isolate themselves for 14 days. The Government also banned cruise ships coming to New Zealand until at least June 30, 2020. Ships within New Zealand already were able to finish their voyages, according to the head of the New Zealand Cruise Association.

Ardern said on Saturday the changes would slow the spread of infection.

"New Zealand has today, relative to other countries, a small number of cases," Ardern said on Saturday. 

"We must plan and prepare for more cases. We must go hard and we must go early. We must do everything we can to protect the health of New Zealanders."

People travelling from the Pacific Islands to New Zealand will be exempt, unless they show symptoms of coronavirus.

Travel restrictions would be reviewed in 16 days, the prime minister said.

Ardern reiterated public health messages to prevent the spread of infection. "Wash your hands," she repeated three times.

People should also stay home and avoid contact with older people if they're sick and stop greeting each other with a handshake or hongi.

It comes after a sixth case of the novel coronavirus was confirmed in Auckland.

A man in his 60s who had recently returned from the United States tested positive for the illness on Friday night.

CRUISE SHIPS POTENTIAL 'DISEASE INCUBATORS'

University of Otago associate professor and public health medicine specialist Brian Cox said it was difficult to contain the spread of infectious diseases on cruise ships as there were often several thousand people in close proximity.

"People are stuck on there so if someone does get infected then it's very hard to contain the infection within a small group on the boat."

In a widely criticised move, Japan quarantined passengers and crew on the Diamond Princess cruise ship, resulting in more than 700 people becoming infected with Covid-19 out of 3711 passengers and crew. 

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"The Japanese experience was a sad lesson that keeping people aboard such a ship just spreads the infection through a large number of people, and the boat becomes, basically, an incubator for spread of the disease," Cox said.

If the suspected case of Covid-19 on the Golden Princess in Akaroa returned a positive result, Cox said in his opinion passengers should be removed from the ship and placed in self-isolation for two weeks. He acknowledged doing this, particularly finding space, would be extremely difficult.

"In a situation where someone is positive for coronavirus on one of these cruise ships in our waters we really have to work out a system of taking everyone off the boat and putting them in isolation for two weeks."

"I think that's the safest thing to do for the fellow passengers on the boat. And I think it would be inhumane to just turn it around and send it back."

LONGER WINTER FOR LOCAL BUSINESS

Darren Angus, who owns three businesses in Akaroa including the Village Inn hotel, said the ban would have been worse if it came earlier in the cruise ship season. 

According to the Akaroa cruise ship schedule, eight cruise ships, including the Diamond Princess, were expected to dock at Akaroa until the end of the season in mid-April. 

"Eight ships in for the next six weeks is going to have an impact," Angus said.

"Fortunately, this is happening toward the end of the season, so when things are sort of slowing down anyway."

The ban would probably mean a longer winter for business, he said. 

He had been busy on Sunday morning dealing with hotel cancellations. He hoped New Zealanders who could not travel overseas for Easter would instead choose somewhere like Akaroa. 

"It is what is, you've just got to crack on and make the best of what you've got. We just don't know what it is we've got at the moment," he said. 

"All you can do is try and keep up-beat and not get dragged down by it."

Akaroa Sailing Cruises owner Ray Shoebridge said he and other tourism operators had all lost out on bookings from Golden Princess passengers, but said it was appropriate passengers were not coming ashore. There had been 15 buses waiting to take passengers to destinations around Canterbury in the morning, all of which departed empty. 

"What would be the alternative? Akaroa becoming the first hub for coronavirus in New Zealand? That would be unthinkable," Shoebridge said.

"Rather than take that risk, we'd rather say so long to Princess Cruises until next season. We'll keep our head above water medically, if not financially."