The new case was alerted to senior Government ministers at 2am today.
The new case - understood to be a young man - has tested positive after being transferred to Waitakere Hospital from North Shore Hospital where he has been receiving treatment for an unrelated condition earlier this week.
The new case was discovered early today - North Shore Hospital is diverting patients elsewhere in response to the discovery.
Associate Minister of Health Ayesha Verrall told Newstalk ZB there are now 22 confirmed community cases in Auckland, up from 21 yesterday. She learned about the new case at 2am today.
The Ministry of Health said people needing emergency care are being diverted from Auckland's North Shore Hospital and Short Stay Surgical Unit from this morning following the positive case.
Director-General of Health Dr Ashley Bloomfield said both the hospital's Emergency Department and the Short Stay Surgical Unit had been closed today. The patient had been in North Shore with an unrelated issue. Verrall did not know the current condition of the young man.
"Given the incubation period of the virus, the DHB has assumed that the person could have been infectious during the admission to North Shore Hospital," said the ministry.
"Diversions to other hospital EDs are in place as the DHB this morning contacts staff and patients who may have been exposed to Covid.
"Affected staff will be stood down and advised to follow public health advice and potentially exposed current patients will be notified and isolated as well as tested in the hospital. Patients already discharged will be followed-up by public health officials.
"The affected parts of the hospital will be deep-cleaned today and then reopened as soon as it is safe to do so. The DHB will be working today to confirm the number of staff and patients affected."
Verrall told Newstalk ZB's Mike Hosking that she could not say if the young man was linked to the other 21 cases.
She could not answer any further questions about new cases - she said that would be announced at 1pm.
"At this stage of an outbreak it's highly likely we will see new cases today. Clearly the Coromandel is a risk area."
Students from two more high schools test positive
Meanwhile, two more Auckland high schools have been caught up in the Covid Delta outbreak as the Government decides today whether to extend the nationwide lockdown - experts are predicting at least one more week in level 4 for the country.
A Northcote College student has been confirmed as having Covid-19, according to an email sent to parents, caregivers and staff by the Auckland Regional Public Health Service. And a student at Lynfield College has also tested positive.
The new cases come as experts predict the Government will likely extend the nationwide lockdown today. Epidemiologist Professor Michael Baker said he would expect at least another week in lockdown as the boundaries of the spread were still not clear.
Auckland and Coromandel are in lockdown for seven days, while the rest of New Zealand was initially locked down for three days, from 11.59pm Tuesday night.
Baker said there were likely to be "quite a few more cases" in coming days given many of the locations of interest were indoors. But the good news everyone was in quarantine was at home, which meant lines of transmission could be broken, he told The AM Show.
He said there was concern that many of those with Covid-19 were young people with very few symptoms and huge social networks.
"One of the key things is all of us with teenage children and young adults in our families... is to explain to them why they are part of this outbreak, why it really matters that they change their behaiviour for the next two or three or four weeks because that's how we're going to get it under control," he said.
"We know that infected people went to a whole lot of indoor environments with very high risk - not just schools but also churches, nightclubs, bars, restaurants - so expect to see quite a few more cases in the next couple of days. That's inevitable."
The outbreak has already affected Avondale College, where a teacher has tested positive, and AUT, where a student was infectious earlier this week.
The Northcote College student was infectious when at school on August 16 and 17, the email said.
All staff and students at Northcote are considered close contacts and have been told to self-isolate at home for 14 days. The North Shore school has about 1200 students.
It's unclear whether the student is one of the already confirmed 22 cases.
Health officials have also added a bus route from Glenfield Mall to Northcote College to their ever-growing locations of interest list. The route (95B or 95C) travelled between the locations from 8.27am to 8.40am on August 17.
The Lynfield College pupil was also infectious while at school on August 16 and 17. Staff and parents of students were notified of the positive case earlier on Thursday evening.
Staff and students there are also being told to self-isolate at home for 14 days.
Again, it is unclear if the student is part of the cases publicly reported by Ministry of Health officials to date.
Lynfield College is located in Mt Roskill and has a roll of about 1800 students.
The new cases come after students and staff at Avondale College were told they would have to quarantine for two weeks after a teacher was identified as having Covid-19 earlier in the week.
A student at the NZ School of Tourism has also been confirmed as having Covid-19. It is unclear whether the student is one of the already announced cases or additional.
The school was unaware of when the student had become infected, the email said. The student had not been on campus since August 10.
Lockdown decision
The Government will today decide whether to extend the national lockdown as a key "piece of the puzzle" fell into place yesterday, crucially linking the current cluster to a border case.
This means officials can more easily encircle the outbreak, but experts say as the number of places of interest swells past 120 - including some with "super-spreader" potential - and the extra threat of Delta, extensions to the lockdowns are likely.
As of Thursday night there were 21 Delta Covid cases in Auckland, including two in hospital.
Twelve have been confirmed as part of the same Auckland cluster. The Herald understands several are relatives.
A further eight are being investigated and are expected to be part of the cluster.
The other - an air crew member - is not expected to be linked because it is a border-related case.
Two people were taken to North Shore Hospital overnight on Wednesday. One had worsening symptoms and the other had underlying conditions. One is in their 20s and one in their 40s.
Bloomfield said five new cases were a family group, and, although they weren't confirmed as part of the cluster, at first glance there was a connection to Avondale College. Interviews were ongoing.
Prime Minister Jacinda Ardern said based on genomic testing, the current cases were a close match with a returnee from Sydney, who arrived on a managed red zone flight on August 7.
They returned a positive result on August 9 and were transferred from the Crowne Plaza to the Jet Park on that same day. They were taken to Middlemore Hospital on August 16.
Additional information could emerge, but "the balance" of evidence gave enough confidence to begin searching for the missing link to the community cases, Ardern said.
Middlemore Hospital was not a line of investigation at this stage because of the timeframe but staff at the other facilities would be retested. Of those staff, 403 were fully vaccinated and the remaining five had received one dose.
Bloomfield said with the likely border link their modelling suggested cases could reach around 50.
There were 362 people categorised as close contacts of positive cases, but by the end of yesterday "well over 1000" people would have been contacted, Bloomfield said.
The Cabinet will meet at 1pm and announce at 3pm whether to extend the three-day lockdown due to end at midnight for most of the country and any variations to the seven-day lockdown for Auckland and Coromandel.
Ardern said the decision would be based around a range of factors including case numbers, the spread and any new information around the connection to the border.
She urged those around the country, particularly in the South Island, to get tested so they could stamp out the possibility of any other outbreaks.
Te Pūnaha Matatini Covid-19 modeller Professor Shaun Hendy said the discovery of a possible link to the border was good news.
"If it holds up under further investigation then the later arrival date means we are looking at a much shorter chain of transmission and fewer cases than the early results suggested."
Finding the link meant there could have been fewer cases circulating in the community, however the speed the cluster is growing at means they still estimate there could be about 100 cases.
