Everyone who attended three services and a wedding at a Mt Roskill church is being asked to get tested after five Covid-19 cases were linked to the venue.
The Mt Roskill Evangelical Fellowship Church cases are yet to be connected to the existing South Auckland cluster, but the chances of them being a new cluster are being downplayed by director general of health Dr Ashley Bloomfield.
Although officials believe they have contained the cluster, the re-appearance of Covid in the New Zealand community over the past month comes as the worldwide number of cases reaches a grim milestone today - 24 million cases and 821,000 deaths.
The services at the Auckland church were on August 8, 9 and 10 and the wedding was on August 7 - all before the region went to alert level 3 on August 12.
"We fully expect it to be linked to the existing cluster. We just haven't got the epidemiological link yet," Bloomfield said yesterday.
"They're like a mini-cluster at the moment."
Church services and weddings can be super-spreader events because they are mainly indoors with large crowds.
But Otago University epidemiologist Professor Michael Baker said the "mini-cluster" didn't necessarily mean there would be a big spike in new cases that were previously undetected.
That was because there had already been more than 200,000 tests since the South Auckland outbreak was detected.
"The chief problem with unconnected cases is that contact-tracing can't find them. That's why the high volume testing is vital to controlling this outbreak," Baker said.
Otago University infectious diseases expert David Murdoch said today genomic testing would reveal any links to the main cluster.
There was "nothing obvious" to reveal a link so far - but genomic testing was a "very powerful tool being deployed in close to real time" that would hopefully prove the link. "We have to wait and see," he told Newstalk ZB's Mike Hosking.
He did not believe that the failure to find the index case - and where the cluster originated - was a major issue. The tightening of procedures, such as border testing, would naturally plug gaps.
The other case of concern is the man in North Shore Hospital, who is linked to the cluster via genome sequencing but how he became infected is still a mystery.
His household and workplace close contacts have so far tested negative.
The Auckland public health unit is looking at a private event he went to at the start of August, which Bloomfield described as "right at the boundary of possibility".
Baker said that was "good news" for signs of the outbreak being contained.
"There's no indication really that there is widespread transmission beyond the known cases at this stage."
He said the timing of the church events - up to four days before the new outbreak was confirmed - underscored the need for Auckland to have gone into alert level 3.
And the type of venue also pushed the case for wearing masks for indoor gatherings.
"This is the way to spread the virus around. We know it from our own experience with our clusters. Mask use at all indoor environments needs to be part of level 2."
Level 2 already requires physical distancing of two metres in public and in retail stores, and one metre in most other environments.
"That's a proxy for not sharing respiratory droplets, but masks do it better," Baker said.
There is no indication at this stage that the Government will mandate wearing face-masks for indoor settings other than public transport at level 2 or higher.
Undetected spread of the virus is now the target of testing - including of people without symptoms - in south and west Auckland.
The Government is aiming for 10,000 tests a day - there were 8559 tests on Tuesday - and Bloomfield encouraged people to get tested today at stations at Ranui library carpark, Randwick Park School, Mt Smart Stadium and Taka He Monu (Tongan Methodist Church) in Point England.
Yesterday there were five new cases of Covid-19 - three in the community and two contained in managed isolation.
The cluster now numbers 108 cases, and there are nine people in hospital with Covid-19, including three in critical condition.
Meanwhile, the Government is under fire for not testing everyone in managed isolation on day three of their 14-day stay.
Auckland University Professor Shaun Hendy, whose team had been providing Covid-19 modelling to the government, said day three testing was important.
"It allows for more effective quarantine of those who test positive but don't show symptoms.
"This reduces the chances of spread to others staying or working in the same isolation facility, thereby cutting the chances of an infected person being released into the community."
The Rydges maintenance worker who has the same strand of Covid-19 as a returnee staying at Rydges - who tested positive on day three - shows how an infection can spread within a facility.
National Party health spokesman Dr Shane Reti added that the public expected a day three test for everyone in managed isolation because that's what ministers, including Prime Minister Jacinda Ardern, had told them.
Health Minister Chris Hipkins said 14 people had tested positive on day 12 of their stay, and all but two of them tested negative on day three.
"This should give the community confidence that no one is coming out of managed isolation or quarantine without a clean bill of health."
He said 15 people had refused a day 12 test, and they had been made to stay in managed isolation for longer.
He did not know how many people had refused a day three test.
Today he will reveal the rules for face masks on public transport that will come into force on Monday.
QR codes will be mandatory on public transport from next Friday. They will be on buses, trains, taxis, ferries and rideshare vehicles, but private vehicles will be exempt.