An Air NZ crew member might have caught Covid-19 in New Zealand before flying to China and testing positive, Covid-19 Response Minister Chris Hipkins says.
"At this point of the investigation, you leave all possibilities open."
Preliminary investigations showed that the person's movements in New Zealand for the past two weeks appear to have been confined to Auckland, he said.
Their circle of close contacts also appears to be "relatively small", though he will receive a further update later this morning.
The person's positive result emerged yesterday, and Prime Minister Jacinda Ardern said they had tested negative on November 18 before testing positive on November 22 as part of routine testing while in China.
Ardern said the person was asymptomatic and was being tested again.
This morning Hipkins said the person had now developed mild symptoms, but the rest of the crew were still asymptomatic.
They were returning to New Zealand, and will all go into isolation when they land at about 6am tomorrow morning.
"Contact tracing has already started for the last couple of weeks for the person's time in New Zealand," Hipkins said.
"They were doing quite a busy international flight schedule during that time, so they spent a lot of time away, but we obviously look at what they were doing while they were here as well."
The person's flight schedule in the past month included flights to Australia and China, he said.
"Coming back from a higher risk place like China - they should be doing a 48-hour stand down and a negative test at the end of the 48 hours before they can go back out into the community.
"We're checking to make sure all those things have happened."
He said genomic sequencing, which has proven to be a vital tool in the Covid-19 response during recent outbreaks, would be done as soon as the crew member landed in New Zealand.
"The whole crew will be isolated and then we'll go from there."
Hipkins said work was under way, given the vaccines that continued to emerge, to decide how much of the population would need to be vaccinated before travel restrictions could be dropped.
"One of things we're looking at is percentage of the population before we can remove all travel restrictions. It doesn't necessarily have to be 100 per cent. We may never get to 100 per cent."
But he said some form of travel restrictions would likely remain in place for the next year to 18 months.
"The sooner we can remove restrictions, the better."
He added that the Ministry of Foreign Affairs and Trade was talking to other countries about an international system to have people certifiably vaccinated.
"We do need to know if someone has been vaccinated or not. We would want to know that as part of our overall protection measures. I imagine that is going to be the subject of a lot of diplomatic discussion."
Part of that could be a technology solution, he said.
The NZ Covid app could not only show whether someone had been tested and the result of that test, but could also show whether someone had been vaccinated, and by which vaccine.
"We're looking at how tech can be used for verification of test results and so on."