Auckland's latest Covid-19 episode will have proven "frustrating" to many - but the snap lockdown was nonetheless ultimately justified, an expert says.
Scientists today welcomed Cabinet's call to move Auckland to alert level 1, and to require masks on public transport across the whole country, at all alert levels.
Covid-19 modeller Professor Michael Plank said the drop down made sense, with a vast number of negative tests now giving officials "good confidence" there wasn't an undetected community outbreak.
"It's frustrating that we haven't got to the bottom of it, and we may never get to it," he said.
"Still, what we've seen is an example of really good response to a situation like this.
"Because when those first community cases initially came to light, it wasn't really clear what we were dealing with - and we could have been dealing with something like the Auckland outbreak.
"By last Wednesday, it was becoming apparent this wasn't the case, and that we had a much small number of cases.
"It might have been frustrating to have had this three-day lockdown in Auckland.
"But over the long term, that's preferable to sitting on your hands and risking a bigger outbreak that then becomes very difficult to control."
Those points were echoed by fellow Te Punaha Matatini modeller Professor Shaun Hendy.
"The week started with the announcement that there with new community cases with only a weak link to the border, much like the Auckland August cluster did," he noted.
"The whole genome sequencing then told us that there was no direct link to any known case at the border, but also that we were dealing with one of the new, more transmissible variants.
"However, a massive test and trace effort quickly contained the relatively small number of secondary cases and gave reassurance that we were not looking at the edges of a much larger cluster like the one we uncovered in August."
Given that the cluster now appeared well contained, and there was no evidence of any larger cluster, he said, it was appropriate that Auckland moved to alert level 1 at midnight.
"This case has shown us that we can't be complacent - Covid will continue to surprise us - but it also shows that when our community is vigilant and our systems are working well that we do have the measure of this virus."
University of Otago epidemiologist Professor Nick Wilson similarly backed today's decision and also thought it "disappointing" that the source of the incursion hadn't been found.
"It's good, at least, that the Government has leveraged this opportunity to get mask-wearing established on public transport across the country, on an ongoing basis."
There was now more than enough evidence to support the need for that wider measure.
University of Auckland aerosol chemist Dr Joel Rindelaub said the latest data showed the widespread use of masks could help reduce transmission of the virus - even if the masks themselves weren't 100 per cent effective.
"Wearing masks is particularly important in indoors areas where there is less air ventilation compared to outdoors. In fact, most super-spreader events have happened in indoor environments," Rindelaub said.
"Thus, wearing masks is a very useful tool in places like public transport, where a small enclosed space with minimal air flow allows for the transfer of tiny aerosol droplets between passengers.
"We have MIQ [managed isolation and quarantine] facilities across the country, so it would make sense to similarly require masks on public transit across the country."
He added that proper masking - and remembering to cover the nose - was also important.
"Since the nasal cavity has many sites where we know the coronavirus likes to attack, it may be a key area for infection and it could be related to loss of smell and taste that so many Covid-19 patients experience."