Prime Minister Jacinda Ardern has foreshadowed a "doubling in cases" of COVID-19, prompting National leader Judith Collins to call for the release of advice on Auckland's drop down alert levels.
The Ministry of Health registered 43 new community COVID-19 cases on Tuesday, all but three in Auckland, despite the city being in lockdown for eight weeks, and it seems the virus is only tightening its grip.
"At the moment, our modellers have suggested that the R value for this outbreak sits between 1.2 and 1.3, so that does suggest that we will continue to see growth in the outbreak at this stage," Ardern said at her 1pm press conference.
The R value represents the number of people that an infected person will pass a virus on to. Measles has an R number of 15 in populations without immunity. That means, on average, one person would spread measles to 15 others.
The original Wuhan strain of COVID-19 had an R value of 2 to 3 but Delta's R value is about 5 to 6 without lockdown and other restrictions, with some researchers suggesting it's even higher.
Last month Auckland University Professor Shaun Hendy, a disease modeller, said the R value of the Delta outbreak was only about .4, but the virus has a long tail often infecting household members, and it's also spreading in some workplaces.
"That is why we are asking everyone to really help us by continuing to follow the restrictions that exist but also by being vaccinated," Ardern said.
"An R value of between 1.2 and 1.3 suggests over a two week period you may see a doubling in cases. But it very much depends on whether we sit closer to 1.2 or 1.3.
"But also we are seeing the impact of vaccinations. They are already affecting the growth in the outbreak and helping to control it and it's why vaccines and following the rules are so important."
Auckland was shifted down from alert level 4 last month despite 22 new community cases reported the day before and against the advice of several experts. Ultimately, the Government had to consider the mental wellbeing of Aucklanders and the financial strain on businesses.
With more businesses able to operate at alert level 3, the virus has been able to transmit via food delivery, taxi services and construction workers.
"Case numbers were trending down but are now clearly on a steady rise since Auckland left level 4. When will the Prime Minister release the health advice relied on to make the decision to reduce restrictions?" Collins said on Tuesday.
"It is clear the eight-week Auckland lockdown is no longer about elimination. So, what is it about, Prime Minister? The concession that we only expect case numbers to grow under current restrictions raises more serious questions for the Prime Minister."
Ardern said Delta has made this outbreak much trickier than dealing with the original Wuhan strain of the coronavirus.
"We have seen cases in workplaces that weren't operating in a level 4 environment. That is true. You heard me talk yesterday about food delivery and taxis and construction sites," she said.
"You'd be hard pressed to find other countries who have managed to completely crush, quickly, Delta outbreaks. It's more transmissible and that poses a lot of challenges for contact tracing.
"Early on we saw that point at which someone became infected and then infected another with a very short window. But I think the research now is suggesting it's roughly three days on average, and so that makes things very hard.
"A second factor is simply where this outbreak has reached. It has reached into communities that have sometimes been hard to reach. It's also reached into vulnerable communities. We know that we've had cases and outbreaks across some members of communities where life is incredibly, incredibly difficult, and I would say COVID is probably not the biggest challenge in their life at the time it reaches them.
"A number of other factors are at play, but that gives you a little bit of flavour on the complexity of this outbreak. For me, the ultimate landing point is that no one is to blame here for the situation in which we find ourselves, other than COVID-19."
Director-General of Health Dr Ashley Bloomfield said while it's "very challenging" dealing with Delta, it's not all bad for New Zealand.
"The cases, it seems like a lot, but they're still relatively low compared with say where things were at a similar point in Melbourne or in Sydney, and the reason is we've had alert level 4 and alert level 3 and the vast majority of people have done what was asked of them," he said.
"Secondly, our teams have been absolutely aggressively testing, tracing and quarantining people. Our teams in managed isolation and quarantine have taken in hundreds, over 1000 people, to care for them and make sure that they are not transmitting in the community."
Dr Bloomfield said the vaccine is our best chance of freedom. Uptake of the Pfizer jab has reduced the outbreak by up to 50 percent, according to some modelling.
Nearly 90 percent of Aucklanders have had at least one dose, with 63 percent fully vaccinated. As for New Zealand as a whole, 2.4 million people are now double-vaxxed.