Auckland City Hospital is asking all staff and patients to get tested to minimise the potential for any spread of Covid 19 stemming from an infected nurse.
Contact tracers yesterday identified 16 close contacts of the nurse but the number of casual contacts is likely much higher as is the risk of transmission with the Delta strain.
The 21-year-old nurse tested positive for Covid on Tuesday night but had worked four shifts in Auckland Hospital's ward 65 during the period where she could have been infectious - the last on Monday.
Auckland District Health Board today sent a memo to all staff asking anyone who worked at Auckland City Hospital on or since August 10 to get a Covid test.
"Testing asymptomatic people in the workplace is one way of helping identify if anybody else unknowingly has Covid-19 and will allow us to respond quickly to any further cases," the staff alert from Alex Pimm, director of patient management services and incident controller, said.
"This is for surveillance testing so you can continue to work as normal after you've had your test. If you have any Covid-19 symptoms or have been advised to isolate by ARPHS please go home and get a test at one of the testing sites in the community."
Those who work on or had been on level 6 of the building were asked to get a test today while other staff could get a swab today or tomorrow.
The hospital was also asking all current patients to get a test.
There was an on-site testing centre for staff but anyone with symptoms was told to go home, isolate and get tested at a community testing station.
The infected nurse was a North Shore resident and was fully vaccinated but could still have spread the virus with health officials saying they do not yet fully know how the Pfizer vaccine limits transmission.
Ward 65 is a general medicine ward and one of eight wards on Level 6 of Auckland Hospital - five of which are for general medicine. Others care for elderly people and cancer patients.
The District Health Board said she worked with elderly patients and was well away from where any patients with Covid-19 could have been.
The nurse is the sister of a teacher at Avondale College who also tested positive and flatted with two others - both of which have the virus as well.
An email sent to Auckland District Health Board staff says a staff member - the nurse -has tested positive for Covid-19.
One of those flatmates is an employee of the 58-year-old Devonport tradesman whose positive result sparked the lockdown.
The father of the nurse and teacher said the diagnosis came as a shock.
"They said they had a tiny cough and slightly irritable throat, but nothing really at all what we've been told to expect. No fever or anything like that at all," he said yesterday.
"They are feeling fine now, not under the weather at all, it was really like a bolt out of the blue."
In an email sent to staff yesterday the DHB acknowledged there was concern about a "hospital outbreak" and it was taking "a number of precautions".
Staff were asked to wear masks at all times in clinical and non-clinical areas and be careful about hand hygiene.
"Please restrict your movements around the hospital. Ideally please go straight to your workplace and stay there. If you can work from home please do so."
The DHB reduced the number of coffee and food outlets and removed seating in public spaces. Staff were asked to bring food from home to reduce hospital movements.
The email was signed by Dr Mike Shepherd, interim director provider services.
As well as working in her ward, it was possible the infected nurse visited one of the seven food outlets or staff areas.
Director general of Health Ashley Bloomfield said 88 per cent of ADHB staff were vaccinated.
On the fully vaccinated Auckland Hospital nurse who has contracted the virus, Hipkins said one of the challenges was that even people who had received both doses of the vaccine could become infected.
"My understanding was this person wasn't showing any symptoms.
"It is possible we're going to pick up cases of people who don't show symptoms."
Using the Covid tracer app and getting a test if you felt unwell would help "run down this virus" and prevent it spreading in the community.