Two Sudima healthcare workers may have caught Covid-19 as infected foreign mariners were transferred from the isolation wing to the quarantine wing of the Christchurch airport hotel.
They could have also caught the virus from particles in the air while they were treating fishermen with Covid-19, a risk that would have been minimised if they had been wearing N95 masks.
Those are among the lines of investigation into how they got infected, incoming Covid-19 Response Minister Chris Hipkins told the Herald.
"Some people when they tested positive were transferred to the quarantine wing and that's something we're looking very closely at.
"Another question is: should they have N95 masks?"
The workers were wearing PPE including medical masks, which protect against infection from droplets that are expelled when a patient coughs, sneezes, talks or sings.
N95 masks protect against aerosol transmission, or "very small particles that can suspend in the air and can be inhaled into the lungs", according to the Health Ministry.
Hipkins said there was no reason to reserve N95 masks for other airborne diseases because there was a lot of supply.
A possible change could be for different PPE use in different environments. N95 masks, for example, might be more suitable in poorly ventilated areas.
He has asked incoming Associate Health Minister and infectious diseases expert Ayesha Verrall to look at the issue.
Infection from surfaces is less common, but is among the methods of potential transmission when patients were transferred to the quarantine wing at the Sudima.
Hipkins pointed to two previous cases of surface transmission in New Zealand: the maintenance worker at Rydges Hotel who is thought to have caught Covid after pushing a contagious elevator button, and the overseas returnee who touched the same rubbish bin lid as a Covid-infected person.
"The wheelie bins [in managed isolation or quarantine (MIQ facilities)] have all been changed to foot-pedal bins, [but] we're always looking for areas where that could happen," Hipkins said.
"I walked through the Wellington Airport when we were making masks compulsory for people on flights, and they had designated bins for face mask disposal where you had to lift the lid of the bin.
"And I thought, 'This is ridiculous. You're increasing the risk.' Someone touches their mask, lifts the lid, puts the mask into the bin, and the next person touches their mask, lifts the lid ... They've replaced them all with foot-pedal bins."
The two Sudima workers are the only current community cases in New Zealand, and so far none of their close contacts have returned a positive result.
There were two new cases to report today, both contained in managed isolation.
'Confident but paranoid'
The border control measures were as strong as ever, Hipkins said, despite the six or seven instances in just over three months where Covid-19 has leaked from a border facility into the community.
Those include the Rydges maintenance worker, the Jet Park nurse, the overseas arrivals who left managed isolation and later tested positive, the port engineer, and each of the two Sudima nurses.
The 179-case August cluster also probably came from a managed isolation or quarantine facility, but there is no evidence.
These have been described by public health experts as failures of infection prevention control.
"No system can be perfect, but we need to face up to the fact that these are failures of infection control," epidemiologist Sir David Skegg said.
"How many wake-up calls do we need?"
But Hipkins said he was not concerned.
"They've all been well contained very quickly and the system's worked as it should," he said.
"We're not repeating the same mistakes again. Whenever something happens, if there's a weakness, the weakness is solved."
He said he was "confident but paranoid".
"It's operating better than it ever has before. The contact tracing's working, the regularised testing is the highest levels it's been at, the MIQs are operating efficiently.
"But paranoid - always looking for where it could go wrong and always being ready to respond quickly if anything happens."
International masters students next cab off rank
Hipkins said the current MIQ capacity of about 12,000 people a month would not expand anytime soon because suitable hotel capacity and the nursing workforce were already maxed out.
More rooms also inherently meant greater risk, he added.
"We've managed to get the risk reasonably contained for the size of operation we've got now. Once you expand the size of the operation, you expand the need to risk-manage it."
But a transtasman bubble would clear 40 per cent of the rooms for other overseas returnees, he said.
"Forty per cent of it at the moment is [travellers coming from] Australia. If we have a safe travel zone with Australia, whenever that might be, it's going to open up a huge amount of capacity."
The Government has already said it wants to reserve 10 per cent of capacity for migrant workers and to welcome back 250 PhD and post-graduate students.
"The next cabs off the rank would be students in existing post-graduate masters programmes, and there's 2000 in that category," said Hipkins, who is also Education Minister.
Once they returned, the tap could be opened to the other 50,000-odd international students who might want to come back, but they'd be prioritised according to what they could bring to New Zealand.
"English language students are shorter duration, so their economic value is lower. There is a reasonable economic value with school students."
Border controls to be fine-tuned, not shaken up
Prime Minister Jacinda Ardern said in a business speech today New Zealand's MIQ capacity is larger than Australia's on a per capita basis.
"Few other countries are even attempting to stop Covid at the border in this way and in the main it is working. But there is also no fool-proof, error-free way of managing a virus."
She appeared to pour cold water on opening up MIQ to private providers - a proposal floated by National and Act.
"There are some basic provisions that we have to have in order to make quarantine work ... Health staff and law enforcement are amongst them. Every health worker we remove from the system, places pressure elsewhere."
Another way to free up MIQ space would be to allow overseas returnees from lower-risk countries to isolate at home.
But Hipkins said that was a risk because people were already testing negative on day 3 in MIQ and then testing positive on day 12.
"It's quite high risk because you increase the number of people they are exposed to."
Taiwan allows isolation at home, but it tracks those people in what Hipkins says is "quite an invasive way".
"They are basically monitoring their people. I'm not enthusiastic about that.
"New Zealanders are very protective of their data, and we've done some public attitudinal research on that and found that New Zealanders would be very reluctant for the Government to record their movements."
A way around that - which the Government is looking at - is for GPS data to be collected on the Covid Tracer app.
"On the Tracer app, it's still your data. Owning your own data is imperative," Hipkins said.
The Apple-Google GPS model incorporated with the app could be trialled with border-facing workers, he said.
MIQ workers are also going to trial the Covid Card, which uses Bluetooth to record other cards in close proximity.
And a Covid Card trial in Rotorua is also about to begin.
It had been delayed, Hipkins said, because of a software problem which meant the cards had to be sourced from a different supplier.
He said the current system needed to be fine-tuned, not shaken up.
Public health experts have previously asked about moving MIQ facilities away from Auckland, where the population is more concentrated, and even using the army facility at Ohakea, which NZ First supported.
But the Government has said Ohakea didn't have suitable facilities, such as separate bathrooms.
Purpose-built facilities were not out of the question, but Hipkins said building them only made sense if there wasn't a vaccine for another couple of years.
"There are some strong vaccination candidates at the moment that are looking reasonably promising," he said.
"If we're talking about being able to re-open up travel more widely in the next two years, you wouldn't be able to justify building purpose-built facilities."
Streamlined public sector response
In the election campaign, the National Party leader Judith Collins proposed a single Border Protection Agency responsible to a single minister, and criticised the Government for its "disorderly and confused response" across multiple ministers and agencies.
Tomorrow Hipkins will be sworn in as the Covid 19 Response Minister, which will include the MIQ responsibility that was previously with Megan Woods.
He also wants to align the public sector's Covid response to improve accountability in a way not too dissimilar to National's proposal.
"Testing still sits with Health. Decisions around allocation sits with the Immigration side of MBIE [Ministry of Business, Innovation and Employment]," he said.
"Some of the lines of decision-making and accountability are still too convoluted, particularly around the border, and we're going to look at how we can streamline and simplify that."
He said there was no plan to make mask-wearing mandatory on public transport because public compliance remained a crucial factor in the ongoing Covid war.
"One of the things we're working very hard on is keeping the public with us, and keeping that [compulsory mask-wearing] as an escalation point when we need it is part of that.
He praised the MIQ workers who put themselves on the line to keep New Zealanders safe.
"It's a tough gig. There's a lot of public anxiety around them. They're putting up with that everyday, friends and family anxious about the work they're doing.
"They do an amazing job."