With the exception of arrivals from the Pacific islands, those coming from every country in the world will be required to self-isolate for a fortnight. It follows the cancellation of the remembrance service scheduled for tomorrow in Christchurch and confirmation of a sixth positive Covid-19 case in New Zealand, a man who had been in the US.

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The New Zealand government has announced a step change in measures to limit the spread of Covid-19, with arrivals from all countries required to self-isolate for a fortnight upon arrival in New Zealand. The measures go into effect from midnight tomorrow, with the Pacific region exempted. Australia is not exempted.

New Zealand will have the strongest restrictions in the world, said Ardern.

In effect, the change means incoming passenger numbers will reduce to a trickle, but the government believes that the public health imperatives outweigh the economic and social implications.

At a media conference in Auckland, Ardern said New Zealand had not seen the volume of cases experienced elsewhere, but needed to “flatten the curve”.

“We must go hard, and we must go early.”

The decision will be reviewed in 16 days, and applies only to passengers, not freight. Ardern also announced there will be exit controls applied to those travelling from New Zealand to Pacific islands. No one who had been out of New Zealand in the last 14 days, in casual or close contact within anyone confirmed as having Covid-19 or showing symptoms of illness would be permitted to travel.

Announcements on guidelines for social gatherings, new support measures for people in self-isolation and a business support package will be announced in the next few days.

Previously the requirement to self-isolate applied only to arrivals from South Korea and Italy, as well as New Zealand citizens and permanent residents who have been in mainland China or Iran. A blanket ban on foreign nationals travelling to New Zealand from China and Iran remains in place.

“As of midnight Sunday every person entering New Zealand, including returning New Zealand citizens and residents, will be required to enter self isolation for 14 days. Everybody,” said Ardern.

“The Pacific are exempted from this measure, but they are the only ones. Anyone from these countries, though, will be required to self isolate should they exhibit any Covid-19 symptoms on arrival in New Zealand.”

(The Pacific is defined as the Cook Islands, the Federated States of Micronesia, Fiji, Kiribati, Nauru, New Caledonia, Niue, Palau, Papua New Guinea, the Republic of Marshall Islands, Samoa, Solomon Islands, Tokelau, Tonga, Tuvalu, Vanuatu & Wallis and Futuna.)

The announcements follow a meeting of the Covid-19 Cabinet Committee, set up to coordinate and direct the government response to the outbreak, as well as a full Cabinet meeting.

At the media conference Ardern held aloft a print out of the gif created for The Spinoff by Siouxsie Wiles and Toby Morris.

“The goal is to ultimately flatten the curve. That doesn’t mean you have no cases. It means the pace at which you receive them is at a rate such that you can make sure people are cared for in the places they need it most, be it with mild to moderate symptoms at home, or be it in critical care if required,” said Ardern.

The decision meant New Zealand would have “the widest ranging and toughest border restrictions of any country in the world. We are also encouraging New Zealanders to avoid all non-essential travel overseas – this helps reduce the risk of a New Zealander bringing Covid-19 in,” said Ardern.

She also announced that all cruise ships would be directed not to come to New Zealand until at least the end of June.

“We do not take these decisions lightly, we know these travel restrictions will place a significant strain on the aviation industry and anticipate some routes will reduce or cease for a period of time,” she said.

More than a million passengers passed through the border at Auckland International Airport alone in January.

The changes come on a day marked by an intensified New Zealand response to the outbreak.

Early this afternoon a planned service to mark a year since 51 people were killed at prayer in two Christchurch mosques was cancelled. Organisers said the event, which had been scheduled for 3pm tomorrow at the Horncastle Arena, would not go ahead owing to the risk of Covid-19.

Just moments after the announcement, the Ministry of Health revealed that New Zealand had its sixth confirmed case of Covid-19, with a 60-year-old man, who had recently returned from the United States, testing positive in Auckland.

The prime minister, Jacinda Ardern, said they had taken “a pragmatic decision” to cancel the Christchurch event. “We’re very saddened to cancel, but in remembering such a terrible tragedy, we shouldn’t create the risk of further harm being done.

In a statement, she said: “The advice we received for this event, is that based on people travelling from different parts of the country and from overseas, if there was a case it could be difficult to trace those who had come into contact with that person, so we are taking a cautious approach.”

Speaking at a press conference this afternoon, Christchurch Mayor Lianne Dalziel said: “My understanding is what changed was very much a focus on this not being a ticketed event and the risks around traceability. So if there was a case then it would be harder to trace all the contacts that were made. That was probably exacerbated because it is hard not to embrace people at a remembrance service. I think if it had been something else it would be much easier to stand back, but your heart naturally goes out to be people and there is a desire, a need to embrace, and that creates a risk situation.

“The health of the community comes first. We were gathering tomorrow to commemorate the worst possible events you could imagine. It would have been worse to have added to it: the fear that it could have acted as a vector.”

Spokespeople for the Al Noor and Linwood mosques said they accepted the decision had been made in the public interest, and would hold small gatherings tomorrow for their own communities and Muslims visiting the city. Al Noor spokesperson Tony Green said they would be “small events with known members and a few invitees”.

The Pasifika event which was to have taken place in Auckland this weekend was yesterday cancelled, but a range of other events, including the St Patrick’s Day parade on Queen Street and Super Rugby games, have proceeded.

Tomorrow’s scheduled service in Auckland has also been cancelled.

The sixth positive test for the coronavirus involves an Auckland man in his 60s who recently returned from the US. He did not require hospital treatment and is in self-isolation at his home.

The Ministry of Health said that because he did not become unwell for more than three days after returning home, they do not believe anyone else on his flight is a close contact.

In a statement, the ministry said: “Once he became unwell, the man did everything right. When friends in the US alerted him to their possible link to a Covid-19 case in the US, on Wednesday he phoned ahead to the GP and told them of his travel history and his symptoms.

“The man was then assessed in his car by his GP, with the GP wearing appropriate protective equipment, and a test swab taken.”

A “handful of close contacts” who were at a church service he attended – at 8.30am on Sunday 8 March at St Mary’s church in East St Papakura – shortly before becoming unwell are being contacted and put into monitored self-isolation.

New research suggests that some people may be able to transmit Covid-19 virus for up to three days before they display symptoms. Writing in The Spinoff yesterday, microbiologist Siouxsie Wiles said: “This is in line with influenza and several other viral infections. It’s obviously a worrying development as it does mean that people may be more infectious in the early stages of Covid-19 than we initially thought.”

As well as the six confirmed cases, there are two other cases considered “probable” – officials believe they have had Covid-19.

Health officials are currently “scaling up” the ability to contact trace individuals who have been able exposed to others with Covid-19, in anticipation of further positive cases.

The ministry statement said: “With regard to concerts and other large gatherings we have coming up, including this weekend the ministry’s advice is to please stay home if you’re unwell.”

In Australia, official guidance is that no public events with more than 500 people in attendance should go ahead.

The White House has performed a handbrake turn in its own approach, with President Trump in recent days banning travel from continental Europe for 30 days and declaring a national emergency as the number of positive cases spiral.

Meanwhile New Zealand First minister Tracey Martin has gone into self-isolation. This follows her recent engagements in Washington DC with Peter Dutton, the Australian minister of immigration, who announced yesterday that he had tested positive for Covid-19.

Anyone feeling unwell should ring Healthline on the dedicated Covid-19 number: 0800 358 5453 or ring their GP.

This story was updated at 4.30pm to include the prime minister’s announcements.