Kiwis are being warned if there was an outbreak of the UK strain of coronavirus in Auckland, a repeat of August's level 3 lockdown probably wouldn't be sufficient to contain it.
The B.1.1.7 variant - estimated to be at least 50 percent more infectious than others - is behind the UK's devastating third wave of COVID-19. It's put the country back into lockdown, with the daily death toll back above 1000 for the first time since April.
"With the old strain if you went on to infect two people, now with this new strain you might infect three," University of Auckland physicist and disease modeller Shaun Hendy told Newshub.
"It's certainly more serious and it could mean we could have a much more rapid spread - obviously that could pose challenges for the way we control the disease."
While it doesn't sound like much, the growth is exponential. For example, if a person on average infects two others, after five transmission chains 32 people are infected; if they infect three, it's 243 - nearly eight times more.
A handful of B.1.1.7 cases have been picked up at the border here. Half of the new cases reported at Thursday's 1pm update were of the new variant.
"We know there's still risks at our borders with the increase in numbers overseas. We're certainly still at risk," said Hendy. "We need to keep scanning, turn on your Bluetooth in the COVID Tracer app and use masks wherever you can."
If we aren't vigilant - and the numbers suggest we're falling short, with only a fraction of adults regularly using the app - we risk another economically devastating level 4 lockdown.
"Potentially a level 3 lockdown would not necessarily be effective. It possibly wouldn't be able to eliminate the disease - so potentially what we're looking at is using a level 4 lockdown," said Hendy.
"You just have to look at what's happening overseas to see just how lucky we are in New Zealand - it's very easy to be complacent here because life looks normal. But it's not normal for people overseas... [Don't] go to work if you have any symptoms at all."
Analysis of the new variant and how it would fare under various lockdown scenarios by University of Calgary researcher Malgorzata Gasperowicz found while a New Zealand level 4 would work, it could potentially take three times longer to stamp out than the original strain. New Zealand spent just over a month at level 4 in March and April, and another few weeks at level 3.
But if we move fast as soon as the first locally transmitted cases are found - like in August - Hendy says it shouldn't take that long. New Zealand was recording double-digit numbers of cases in March before the alert levels were even made public, let alone enacted - but in August, Auckland went into level 3 the day after the first handful of cases were detected.
"The good thing is we know that level 4 is very effective and based on what we learnt from March and April, we think that would be good enough to eliminate the disease," said Dr Hendy.
New Zealand's strict approach to COVID-19 has been lauded worldwide, resulting in fewer deaths and better economic recovery than in nations which either moved too slow or not hard enough.