* 148 cases, more than 460 events at 340 locations - hospital emergency department worker tests positive
* New locations of interest include three more supermarkets, two Farmers, another university campus
* 'NZ can't do that': Aussie PM Scott Morrison likens elimination strategy to living in a cave
* Claire Trevett: Is the PM chasing rainbows or can she stamp out Delta?
* Rising Black Caps star tests positive for Covid-19
* Readers' questions: Ask us anything on Covid
Experts are questioning whether there has been any "leakiness in lockdown", and are urging clarity on the details of the so-far 148 positive cases in New Zealand's Delta outbreak.
At the same time, they believe New Zealand's elimination strategy - and nationwide level-4 lockdown - remains the best option to combat Delta, despite criticism from Australian Prime Minister Scott Morrison who says the elimination strategy is "absurd" and like "living in a cave".
The Herald also revealed today that Auckland's surging Covid infections are causing a quarantine facility backlog, with infected people waiting more than 24 hours for admission.
Prime Minister Jacinda Ardern told Coast FM she wasn't "too fussed" by what the Australian PM had said and all the decisions made over the past 18 months were about New Zealand and not what other countries thought.
Ardern said New Zealand needed to have a good number of people vaccinated across all the regions and age groups.
"We can't live for lockdown forever and we don't intend to."
Ardern said there was a lot of discussion and debate around booster shots but not a clear conclusion on them yet.
"We are still in a place where there's still a lot of debate among the experts and immunologists about the booster shots."
But New Zealand was keeping its options open and keeping the conversation with the pharmaceutical companies if it did need them in the new year.
Ardern said even if they did move managed isolation facilities outside Auckland, a workforce was still required to look after the 4000 to 5000 people a fortnight who were in MIQ.
"So as you can imagine literally hundreds, thousands of people working to support those facilities so even if you move them out of a city you still require a huge workforce and they come from somewhere. That's why we vaccinate, we test frequently, we do everything to reduce down the risk."
She said work was being done to think about the role of managed isolation going forward and if they needed to change the way they used it.
Deputy Prime Minister Grant Robertson also rejected Morrison's comments, saying the elimination strategy had given New Zealand one of the strongest economic responses and one of the lowest mortality rates in the world.
"I just don't see it the way that Scott Morrison and others are presenting it and certainly every public health expert I speak to says that what we're doing right now is exactly the right strategy for New Zealand," Robertson told Newstalk ZB's Mike Hosking.
The number of Covid cases is predicted to rise dramatically in coming days with just half of the highest-risk contacts having returned their test results.
The vast majority of these cases were infected prior to lockdown, but the Government is also unable to yet confirm if the virus has been spreading under lockdown.
Director general of health Dr Ashley Bloomfield said "some" cases had been infected since lockdown began last Wednesday.
Most of these were close contacts of the cases, most in the same households, however he was unable to confirm if any had spread outside their bubbles, or if any close contacts were essential workers.
Experts are calling on the Government to identify and release this information to the public as soon as it can, given lockdown spread will be the key determinant of whether the outbreak is being brought under control.
Otago University epidemiologist Professor Michael Baker said it would be useful to see the Government classify cases as those that were in the community before lockdown, those that had been detected while at home, and those that were among essential workers still operating under alert level 4.
"What we really want to know is if there are any unsuspected cases occurring in the community that don't have a connection to cases reported now, which could suggest some leakiness in lockdown."
Fellow modeller Professor Shaun Hendy said they were now estimating the outbreak could swell to 1000 cases.
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Robertson said hundreds of contact tracers were conscripted to bolster the permanent public health force - to help get tests done and results back as quickly as possible. He told Hosking that 600 were being trained up to meet the demand under Delta.
There was now a 48-hour timeframe to make contact with those affected.
'The alternatives are grim'
University of Canterbury Covid-19 modeller Dr Michael Plank said some spread should be expected within households during lockdown, but the most important factor was to prevent spread between bubbles.
Plank said this morning there was still testing to get through, with a delay between those wanting a test and their results. He told Newstalk ZB's Mike Hosking contacts were being chased down and that the public had to be patient.
He remained confident that the elimination strategy was the right course to take. It had served the community well to date.
Otherwise, he said, "the alternatives are grim", including rolling lockdowns lasting months like in Australia and other countries.
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He said it would be several weeks before we could really start to see if the elimination strategy needed revising.
"I think if we get to that stage we'll have a clear picture by then of how we're tracking and if elimination is possible and how long it would take to get there."
Baker told RNZ today it was concerning news that a nurse at Middlemore Hospital had tested positive for Covid.
He said although the staff member was fully vaccinated, they could have picked up the virus another way - not necessarily while at work. "They could've easily been infected in other activities."
It was a possibility, for example, that the nurse was a part of the largest sub-cluster connected to the Assembly of God church in Māngere, Baker said.
"I'm optimistic that we will get on top of this," Baker said of the virus.
Referring to Morrison's comments about the absurdity of eliminating the Delta Covid strain, Baker said people needed to remember that that exact thing was being achieved still in some countries and even states in Australia.
"It's largely a political statement. Elimination is a political choice," Baker said of Morrison's comments.
Asked whether New Zealand should still "stay the course", working to eliminate the Delta strain in the community, Baker agreed, acknowledging that the country had done it before. "I'm confident it will be achieved again in New Zealand."
Robertson told Hosking that experts advised elimination was the best strategy to pursue, coupled with high vaccination. "I don't see it the same way that Scott Morrison is seeing it."
Meanwhile, Robertson said he expected to see daily totals climb of businesses seeking the wage subsidy. At the moment it was primarily small businesses that had sought assistance.
Robertson said money had been set aside for the wage subsidy. "The cash is on hand if we need to use it," he said.
Because the economy had rebounded so well after last year's lockdown, debt levels were lower than expected.
Associate Health Minister Peeni Henare told TVNZ today he could not give any updates as "none of the fresh information had been received" in his inbox. He had no information about new locations of interest either.
In regards to an error in which saline is believed to have been administered to five people instead of the vaccine, Henare said an investigation was under way to establish what had happened - whether it was human error or a process issue.
He said officials were "prioritising it" and said he thought those affected had been told. He said it was important people were confident about their vaccines.
Henare rejected criticisms of the rollout.
"We are in a good position."
There were 41 new cases announced Tuesday, including 38 in Auckland, and three in Wellington. There are now 148 confirmed cases in the whole cluster, with 11 cases in Wellington and the rest in Auckland.
Auckland University of Technology confirmed nine cases of Covid-19 and a fully vaccinated health worker was confirmed as a positive case late Tuesday at Middlemore Hospital in the ED department.
The ED remained open and safety precautions were being followed, the Counties Manukau DHB said.
Bloomfield and other health officials appeared with Covid-19 Response Minister Chris Hipkins on Tuesday before the health select committee to answer questions from Opposition MPs.
Public Health director Dr Caroline McElnay revealed about half of the highest risk contacts were still yet to have their test results returned.
There were 369 close plus contacts, 51 per cent of whom had returned test results, and 11 per cent were positive, she said.
There were 14,967 close contacts, 56 per cent had returned test results, and 0.2 per cent were positive.
And there were 405 casual plus contacts, about half of whom had been tested, with no positive results so far.
Bloomfield said cases were increasingly coming from locations of interest or from close contacts, rather than from people who were infected pre-lockdown.
Eighty-nine of the 148 total cases have been epidemiologically linked, and while the other 59 cases were being investigated, Bloomfield said there was nothing to suggest at the moment they were part of a separate chain of transmission.
One of the cases is an Auckland MIQ worker, but they had caught the virus as a contact of an existing case rather than being suspected of being the potential source.
It was still not known how the virus had originally spread from the Crowne Plaza MIQ to spark the latest outbreak, but two key potential contacts had been identified.
Bloomfield revealed the number of cases in major sub clusters: 58 cases in the Assembly of God Church service in Māngere, and 23 cases in the Birkdale group.
He said there were six sub clusters in total and the other four had far fewer cases.
The church sub cluster, which included six people in Wellington, included people who had been at the August 15 service and their close contacts.
Bloomfield said 27 different church groups took part in the service, but the total number of people at the service was yet to be determined. More than 500 people have been tested.
While there was an increase in the number of cases today, there hadn't been an exponential increase, and if the lockdown was working, case numbers would peak in the coming days, Bloomfield said.
Around two-thirds of people infected in New Zealand's Delta outbreak are younger than 30. The youngest case in the outbreak so far is less than 1.
About 70 per cent of cases in the current outbreak were of Pasifika ethnicity, largely as a result of the sub-cluster of about 58 cases linked to the Assembly of God Church (AOG) of Samoa in Mangere. About 20 per cent were Pākehā.
Dr Debbie Ryan, of Pacific Perspectives, said reports that Pacific people accounted for more than half of the cases in the outbreak - yet just 7 per cent of the population - were "depressingly familiar".
"No doubt we will get through the current crisis. Pacific communities and health providers and health workers have again pulled together brilliantly to do what is required," Ryan said.
"But we need a circuit breaker to address these unacceptable disparities."
More than 9000 contacts had been contacted overall and were self-isolating, while almost 900 frontline contact-tracers were working on the pandemic response.
The Ministry of Health has now reported 439 visits to 326 separate locations of interest.
Contact tracing capacity has also come into the spotlight, as almost 16,000 contacts have been identified, but half of them are still awaiting test results.
A review by public health experts - as part of the independent advisory group led by Sir Brian Roche - into the February cases found a ministry reluctant to increase surge capacity for contact-tracing, and an unwillingness to stress-test the system or do scenario-planning.
It said this contributed to ongoing uncertainty about the system's ability to handle a large outbreak.
Bloomfield rejected how the ministry was portrayed.
"That's not a view I did or do hold, that we didn't need to continue to build surge capacity," Bloomfield told the committee.
- additional reporting Jamie Morton, Derek Cheng