An intermediate infection is the likely link between the Grand Millennium hotel's Covid infections among Case A and B, epidemiologist Michael Baker says.
Meanwhile health officials have today released more locations of interest visited by one of the new Covid cases linked to staff at the Grand Millennium MIQ hotel.
The businesses were visited by the security guard who contracted Covid, known as Case B.
The new locations are:
• Local Barber Mt Roskill South, April 7 (2pm - 4pm)
• Funtech, Queen St, March 29 (5.20pm - 6.25pm)
The previously identified locations of interest are:
• Bikanervala Bakery, White Swan Rd - April 7 - 1.30pm to 2.30pm
• Bake and Beans, 1484 Dominion Rd – April 1, April 2, April 6 - 4.30pm to 5.30pm
• Terminus Dairy in Dominion Rd, March 29, March 31; April 1, April 6 and April 7 (all times 4.30pm - 5.30pm for each of the days)
• White Swan Mobile, 151 White Swan Rd – March 29 - 3.30pm to 4.50pm
Anyone at these businesses at the specified times are considered casual contacts. If you have had any Covid-19 symptoms in the past 14 days you should stay home and call Healthline (0800 358 5453).
A third positive Covid case, dubbed Case C, at the managed isolation facility was announced last night - an employee at the facility who was a close contact and colleague of the 24-year-old security guard who tested positive last week, known as Case B.
Case C worked one Easter shift with Case B.
Both are genomically linked to Case A, a cleaner who tested positive on March 21. The Ministry of Health said recently the cases were connected to a person who returned to New Zealand on March 13.
Given the 18-day period between Case A and B testing positive and the virus' roughly 10-day infectious period, Baker estimated another undetected case had passed the virus from Case A to B.
"Given that interval, it's hard to imagine there not being an intermediate case," he said.
He wondered whether an intermediate case at the Grand Millennium may have infected both Case A and B, but said this was unlikely given the length of time between positive test results.
Baker saw similarities in this infection incident with Auckland's August and February clusters, as well as the infection of two Defence Force staff in November.
"I think there's at least three well-documented examples where there were obvious undetected intermediate cases."
CCTV footage was being examined to see whether there was any contact between Case A and B. Baker said the level of concern regarding these recent cases was not overly high, but that the unknown nature of the infection conveyed importance on the current investigation.
"The question is, 'Who were they, did they have the potential to infect anyone else and are there any other unseen chains of transmission'?"
Like with previous clusters, Baker warned the link between Case A and B may never be known.
"We'll never know in some instances and it's always a bit disappointing but the trail has gone cold."
Director general of health Dr Ashley Bloomfield told RNZ today he is awaiting information on the vaccination status of the latest case but he "would have hoped that they would have been vaccinated by now".
He said 80 per cent of workers at the security company where both Case B and C are employed had been vaccinated. Case B was not vaccinated prior to his infection.
"There was a clear expectation that people working in the frontline at the border do get vaccinated or there has to be other options looked at for them," he said.
On three cases coming from the same managed isolation facility, Bloomfield said: "There's an issue."
"Last week when we got this case on Thursday we immediately got our MBIE teams and health teams together to work out what else is going on potentially in this hotel and we've convened the technical advisory group to give further advice there."
No further returnees are being hosted at the Grand Millennium Hotel, he said.
There are 15 total close contacts of Case B still isolating. They will have two tests during their 14-day isolation stay.
In the wake of the security guard and cleaner's positive results, the ministry said an out-of-cycle Infection Prevention and Control audit of the hotel would be carried out, similar to that previously done at both the Pullman and the Grand Mercure facilities.
Meanwhile, four new locations of interest in Mt Roskill were released recently in relation to Case B.
They are: Bikanervala Bakery, Terminus Dairy, White Swan Mobile and Bake and Beans. They were visited at various times between March 29 and April 7.
• Bikanervala Bakery, White Swan Rd - April 7 - 1.30pm to 2.30pm
• Bake and Beans, 1484 Dominion Rd – April 1, April 2, April 6 - 4.30pm to 5.30pm
• Terminus Dairy, 1484 Dominion Rd – March 31, April 1, April 6, April 7 - 4.30pm to 5.30pm
• White Swan Mobile, 151 White Swan Rd – March 29 - 3.30pm to 4.30pm
Anyone at these locations during the relevant time periods is considered a casual contact and should monitor for symptoms for 14 days after exposure.
If you become unwell or develop symptoms, call Healthline, get tested and stay at home until you get a negative test result.
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