Ashley Bloomfield says a possible link from a case in the Māngere church subcluster to the traveller in the Crowne Plaza has been identified, which could solve the issue of any missing transmission links in the whole outbreak.
The director general of health also confirmed to the Herald this morning that while there have been more cases since yesterday's update, none so far are outside Auckland.
The Crowne Plaza has been the focus of the source of the outbreak because of genomic sequencing results matching a case who travelled from Sydney, who arrived here on August 7.
Bloomfield said that health officials were getting closer to tracing how the outbreak started, with the earliest onset of symptoms being on August 10.
"This is someone who is one of our quite early cases, who we think is the most closely connected to the Crowne Plaza at this point in time."
There are two potential areas in the Crowne Plaza where members of the public can share airspace with those in isolation: one is near the atrium at the entrance, and another is a public walkway by the returnees' exercise area.
But Bloomfield said the place where transmission might have taken place wasn't the Crowne Plaza, nor was it a nearby vaccination centre.
"They were in a place where they may have been exposed to the virus - I don't have the detail - very early on, on the 9th or 10th [of August].
"This is someone who is connected to the Assembly of God Māngere cluster, but also has a number of household contacts who are also infected as well."
A connection could mean that the person in the AOG subcluster was infected by the index case, which would mean there are no missing links in the chain of infection.
"It could have been a direct link - that's what's being looked at," Bloomfield said.
"We've had this before where we've never quite been able to nail the exact transmission time and place. But we're pretty close now, and it [may explain] how the outbreak developed out from there."
He added that a link may never be confirmed, just as a link to the border was never definitively established in the February outbreak, or in the August outbreak last year.
No issues have been identified in reviews of the Crowne Plaza's systems - the most recent one was in June - to prevent leakage of the virus into the community.
Work is expected to finish today to close the gap between the top of a perspex barrier in the hotel's atrium and the ceiling - which National Party Covid-19 spokesman Chris Bishop says is contrary to the lack of any safety issues identified.
Yesterday Covid-19 Response Minister Chris Hipkins said that the work was planned before the current outbreak, and there was no evidence so far to suggest the atrium was where the virus had leaked into the community.
Contact-tracing preparation under scrutiny
Bloomfield said the high amounts of testing in Auckland meant that officials were "getting close to understanding the perimeter of it".
There was still the issue of close contacts who were yet to be reached; at 4pm yesterday, these numbered almost 8000.
Bloomfield said they were being contacted "very quickly" and should all be worked through in the next day or two.
The ministry won't have a sense of whether any of them were essential workers or if they had been at any higher interest locations - for example, any connected to any subcluster - until they've been contacted.
"Those are the three critical bits of information, and particularly for our new cases: are they an essential worker, can we link them to existing clusters or households, and were they out and about in the community while potentially infectious."
Bloomfield said he hoped to be able to provide some information at the 1pm press conference today about whether there had been any transmission since the lockdown started.
The ministry's contact-tracing preparation for a Delta outbreak has come under scrutiny, given the number of contacts still to be contacted, and how the workforce has been urgently bolstered by seconding workers across government into contact-tracing roles.
Before the outbreak, the ministry said it had standing capacity to trace 1000 contacts for 180 new daily cases, with surge capacity to trace 6000 contacts per day.
But with 22,000 contacts for 210 cases yesterday, the number of contacts per case was almost double what the ministry had expected.
Bloomfield said the ministry hadn't underestimated the number of contacts per case in a Delta-world.
"Not so much that we underestimated, but the approach we have taken with Auckland Regional Public Health is to go very broad with the definition of who's a close contact.
"The reason we've really scaled up the additional contact-tracing capacity is because - unlike for casual contacts - close contacts require daily check-ins for 14 days, and testing and follow up of results."
Asked why it had taken six days to second staff from across government, he said the workforce could handle the initial calls, but more staff were needed for the follow up calls.
Frontline health workers required to be vaccinated?
The Herald revealed today that the response to the Delta outbreak had been hampered because Auckland and Waikato DHBs were flying blind about who among their staff were vaccinated.
The ministry urgently sought advice from the Privacy Commissioner and decided to link staff records with their vaccination status, given the seriousness of the threat of the outbreak.
DHBs have also been asked to keep a record of which staff members are vaccinated, which requires the worker's consent.
The Government is considering whether to make vaccination mandatory for health workers who come into contact with Covid-19 patients, as is required in overseas jurisdictions including Canada and France.
"We've been asked to and have given advice around whether - and if so which - groups of health workers should be required to be vaccinated," Bloomfield said.
"There are very good reasons why I think frontline health workers should be vaccinated to protect themselves, their patients and whanau, and also their colleagues.
"We've given our advice, and that's with the Government for a decision."
Quarantining cases at home an option
With 210 cases in the outbreak so far and 36 MIQ cases, the quarantine system is under pressure.
There are already cases that have been waiting more than 24 hours to be taken to the Jet Park quarantine facility because of a lack of enough safe transporting services.
Covid-19 modeller Professor Shaun Hendy is now predicting there may be 1000 cases in this outbreak.
Bloomfield said some MIQ facilities can be converted to quarantine facilities, but he has also asked each DHB to plan for managing cases in their homes.
"We have done this before and sometimes people don't go into quarantine, for example if they have physical issues around support needs, or if they've got a disability. They are looked after in their own home.
"So all DHBs are looking at what arrangements they could put in place to look after cases in the home, should that be required."
There may also be people in MIQ who are unable to leave the facilities because of a lack of transport or flights.
"I don't know anything about that, but it would seem quite possible because of the challenge around very few flights," Bloomfield said.
"But I'm sure that MIQ facilities will be working with individuals to organise transport arrangements."
He conceded that could translate into fewer MIQ rooms available.
"It may well, and there is real pressure, and there was already pressure on managed isolation.
"That's one of the reasons why MBIE isn't releasing [MIQ] vouchers just at the moment - and because they've converted one of their facilities to take cases from the community into quarantine if required."