Speaking to Checkpoint on Thursday evening, Minister of Health Chris Hipkins said it was now thought the virus may have been passed on when the two were in the same lift at separate times, but minutes apart, on July 28.
He said in some cases it may not be possible for workers and those in isolation to have designated separate lifts, but this would be considered as part of investigations into how the transmission occurred.
Whether the man and woman each wore masks in the lift was also still to be checked.
He said the possibility the virus was picked up in the empty lift doesn't necessarily challenge the ministry's definition of what a "close contact" to a case is.
Close contacts of someone who tested positive for the virus are prioritised for testing, while "casual contacts" are only tested if they display symptoms of the virus.
Hipkins said, at the moment, there was not enough testing capacity to test all casual contacts, though more testing could be considered if testing technology developed so more tests could be carried out faster.
"You still have to work on a risk-based framework. One of the things we say to casual contacts is that they are at a heightened risk, so you should be much more aware of your symptoms.
"We wouldn't necessarily test everyone who was on a plane with a positive case, but we would test everyone who was sitting near them. And we would tell everybody who was on that plane to please keep an eye out and make sure that if you exhibit any symptoms that you get a test.
"There's still some element of risk there, because they may still touch the same surfaces, and things like that. We've never said there's no risk for casual contacts, that's the reason why we identify them."
Asked whether this case meant practices and risk definitions need to be updated, he said practices and protocols were constantly being adapted as more was learned about the virus here and overseas, but details about this case were still being sought.
"The investigation's still ongoing, and it may well be linked back to the main cluster. We reveal what we know at the time, we've made that commitment, and at the moment there's still a lot of questions around that case."
Different strains, different characteristics
Hipkins said the Auckland cluster strain, called B111, seems to act differently to the most widespread strain that was in the country earlier this year.
"The B111 does seem to be reasonably infectious, in that people show symptoms reasonably soon after exposure to it.
"So that differs a bit to some of the ones we were dealing with earlier on, where there was often quite a gap there."
When viruses produce symptoms earlier in the infectious period it can help those carrying them to take action to get diagnosed and isolate themselves earlier, which can help slow transmission.
Auckland schools return announcement expected
A decision about when Auckland students can return to school is expected to be made early next week, and the government expected to give schools and families some warning ahead of the chosen date, Hipkins said.
"That [decision's] more likely to be on Monday after we've made the decision about what's happening with Auckland."
Questions over Canterbury DHB
Hipkins said he was seeking more information about unrest over executive team resignations, a mounting budget deficit and staff protests at Canterbury DHB.
He plans to speak with DHB chief executive David Meates, and its board chair Sir John Hansen soon, but would not be drawn over whether government intervention into the situation was needed.
