COVID-19 modelling experts warn the highly-transmissible Omicron variant poses a serious risk to a largely unrestricted summer.
Thirteen cases of the variant have now been picked up in managed isolation and quarantine.
The first one was on Thursday, then another on Friday, then three more were announced, then four more, then yesterday five further cases of Omicron were notified by the Ministry of Health. The cases are in mangaed isolation (MIQ) in Auckland and Christchurch.
More cases would keep arriving at the border, increasing the chance one would leak out into the community, Te Pūnaha Matatini complex systems researcher Dion O'Neale said.
"At the moment most of those [MIQ] infections will be Omicron from now on, purely because Omicron is most of the cases in countries that people are coming back to New Zealand from," Dr O'Neale said. "At some point, it does become a matter of time until that gets out into the community."
With Omicron, Dr O'Neale said some environments clearly posed a high risk, such as nightclubs and concerts. But even environments like restaurants and cafes could be the site of dozens of infections if a positive case attended.
"It's the case of having lots of small events where people might be infecting dozens of people at a time. That's a way that you really quickly get things out of control.
"Orange, as a traffic light level as part of the COVID Protection Framework, isn't really fit for purpose if we have Omicron in the community."
He said an outbreak here would probably mirror what's happened in New South Wales.
Two weeks ago the Australian state had about 200 cases a day, while on Sunday it recorded 2566. The state's health authorities believe most of the cases are Omicron.
Even a single case here could jeopardise some of our hard-fought freedoms, COVID modeller Michael Plank said. It would depend if the case had a clear link to the border or had been in the community.
If the variant became established, Prof Plank would expect it would spread "extremely quickly", as even fully vaccinated people were not as protected as with Delta.
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"The ability of Omicron to infect people who have had both doses of the vaccine is significantly higher than for Delta".
There have been over 10,000 Delta cases in this outbreak, of which Māori make up nearly half.
Sue Crengle of Te Rōpū Whakakaupapa Urutā, the National Māori Pandemic group, said Omicron posed another risk and community cases should trigger action.
"I think we should use a heightened level of restrictions, especially if it's in regions where there are high numbers of Māori and there are lower vaccination rates," Dr Crengle said.
Auckland Business Chamber chief executive Michael Barnett said any stronger restrictions would not be tolerated by businesses or even, in his view, regular Aucklanders.
"I don't think Auckland would be prepared to take any further constraints, constrictions. They've been in lockdown for what, 115, 120 days?
"They're tired of it.
"I think [the] Government should be making it abundantly clear what are the conditions under which they would impose any constraints," Barnett said.
The Ministry of Health said it and the MIQ teams had been "carefully planning" for Omicron cases at the border.
All passengers on flights with Omicron cases must spend all 10 days at a managed isolation facility, rather than seven in MIQ and three in-home isolation like other arrivals.
