Health Minister Chris Hipkins says health officials are confident they've reached almost everyone with links to the Auckland COVID-19 cluster.
Only five new cases in the community were reported on Wednesday, bringing the total to 75, Hipkins telling The AM Show to expect "similar" numbers at Thursday's 1pm daily briefing.
"The growth in that cluster is slowing - we'll get the exact numbers later in the morning and release those at one o'clock. We do seem to be starting to reach the outer perimeter of this cluster, which is of course what the whole contact tracing system is designed to do."
Only one case out of the 75 is not linked to the cluster - a worker at the Rydges Hotel managed isolation facility - and their infection doesn't appear to have started a second cluster.
The apparent success in containing the larger outbreak comes amid criticism of the lack of testing of staff working at the isolation and quarantine facilities. Despite Hipkins saying an order was made in July that all should undergo regular testing, it later emerged this wasn't happening.
Hipkins said no one in particular is to blame, and more staff were likely getting tested than statistics suggested.
"In some cases they were being tested, it just wasn't being recorded - people who were being tested by their GP or their community-based assessment clinic... they were just recorded as part of the overall number of tests every day, and we weren't getting that broken down.
"So when people were saying 'I've been tested', if someone says 'I've been tested' you have to believe that they've been tested. That's not the sort of thing people generally lie about, particularly when they graphically describe the process to you. When people are saying that, you have to have some confidence that they have actually been tested... I don't think there's any one person or any one thing that's particularly to blame here. I think there have been some systemic issues that have taken a while to work through."
He also said even if every single worker had been getting tested regularly, the current outbreak wouldn't have been prevented. It's source remains a mystery, but is genetically similar to strains in the UK and Australia. The genome of the virus found in the isolated case has been linked to a person who arrived from the US who stayed at the same facility, but there was no person-to-person contact.
"There's no evidence to suggest that testing in managed isolation, quarantine and at the border would have prevented this current outbreak."
The low rate of positive tests suggests there isn't a wider outbreak, Hipkins said, raising hopes Auckland could come out of alert level 3 earlier than the original plan, which was Thursday next week.
"Indications are the contact tracing system is working as it's designed to work."