"One of the reasons we are all in lockdown and not just Auckland or the Coromandel or those places of interest, is because we haven't yet answered that question of where it started," Prime Minister Jacinda Ardern said on Wednesday. 

"The reason that's important, is because every case we have that comes through our managed isolation facilities, we put through that same process, which means that if we have a case in the community, we can potentially use genome sequencing to match it and hopefully find the chain.

"The results that have come back from our case yesterday tell us two things. First, that we are dealing with the Delta variant. The second thing it tells us is that it is linked to the current genome sequencing of cases in the New South Wales outbreak.

"Our case has originated in Australia. Now, the job we have is to work through how and when it got here."

Ardern said MIQ facilities are the "natural place to look", considering there has been three positive cases from Sydney in MIQ since 1 July - one detected on 9 August on their day one test, and two on 14 August on their day three tests. 

"These cases are currently being genome sequenced as we speak and we expect the results later tonight to tell us if they are a match or not a match," Ardern said. 

"I can confirm that for every other case we've had at the border which is sequenced already, there are no matches to this case."

But if the infection didn't come from MIQ, then it had to have come through the trans-Tasman bubble, and the Government isn't ruling that out. 

The Government closed the quarantine-free trans-Tasman bubble on 23 July after daily case numbers began rapidly increasing in New South Wales, and popping up in other parts of the country. 

Every passenger had requirements on them before they entered New Zealand in the one week window the Government gave New Zealanders to return home. 

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Those outside of Victoria and New South Wales were able to get on flights and not go through managed isolation, but they had to provide evidence of a negative pre-departure test.

Those in New South Wales had to spend 14 days in managed isolation upon their return, while those travelling from Victoria were told to self-isolate at home, with similar testing requirements to those in MIQ. 

"Travellers from Victoria had to have two tests - one before they departed and one after three days in isolation when they returned. I can report that everyone was compliant with those requirements," Ardern said. 

"For everyone else from other parts of Australia, they had to have a negative test and we had 100 percent compliance with that during the week that people returned to New Zealand.

"Despite that, we are drawing down the list of all travellers from Australia into New Zealand through that period, in preparation to contact them again, should we find that this case is not linked to the current cases we have at our managed isolation facilities."

Ardern suggested it would have been difficult to get COVID-19 into New Zealand undetected.

"It would've required someone to get around the border controls that were in place in Australia, it would've required them to get past both Immigration and Customs controls and the testing we had on departure and arrival and checking of testing."

Another possibility is that the virus could have been spread at a hospital. There are now seven community cases, and one of them - a contact of the Devonport case's co-worker - works at Auckland Hospital. 

But Ardern and Director-General of Health Dr Ashley Bloomfield don't seem to think that's how the virus has been passed on. 

"We have been discussing any contact with COVID cases across our hospitals. We have not had a New South Wales COVID case at Auckland Hospital. We have had one in hospital but not that one," Ardern said. 

"Some of the timeframes don't quite work there. We did have a New South Wales case admitted to hospital, but the proximity to that admission to hospital and the cases we have now are very close together."

Dr Bloomfield added: "We mentioned this week a case had been transferred from Jet Park to Middlemore Hospital. That was one of the people who had travelled to New South Wales. It doesn't fit with the timeframes."

Ardern said there should be more clarity as the week progresses. 

"We moved very early on in the New South Wales outbreak, even when they had quite small numbers. Customs is already drawing down manifests and I think there is good wisdom in us going back beyond just when we had those red zone flights returning.

"Once we get the genome sequencing back, it'll either tell us we've got a case linked to managed isolation or not."