Epidemiologist Professor Michael Baker says the origin of the latest trio of Covid-19 community cases in New Zealand is likely one of two scenarios.
Auckland was shifted to Alert Level 3 and the rest of New Zealand moved to Level 2 after three community cases - a father, mother and daughter - were discovered in South Auckland yesterday morning.
Baker told 1 NEWS today the cases could have either come from a breach at the border or is an unknown transmission that was already present in the community, with his beliefs currently lying with the first option.
"Given what we know about how Covid-19 is transmitted, it's almost invariably between people in indoor environments on respiratory droplets and aerosols so your number one source is always going to be some connection to the airport that has infected this family," Baker said.
Baker said the fact there is a clear link between the cases and the airport - the mother's job in an airline laundry and catering company - means the first option is much more likely.
"The most likely hypothesis I've heard mentioned is that this woman works in a facility that also includes staff who work airside at the airport so they'd have potential contact with infected people," he explained.
"That would be a good, working hypothesis you'd want to check out ... if she shared an indoor environment with someone that was carrying the virus, she could easily be infected."
The second option, an unknown transmission, would be much more problematic Baker said, with last year's August outbreak in Auckland which resulted in 179 cases and three deaths an example.
"I think that's the big concern and that's why there's such a strong focus on this short, sharp lockdown in Auckland to try and rule out the idea that this might be the beginning of a community outbreak," Baker added.
"The big worry there is that if this family was infected as part of what might be a larger outbreak, there will be other cases out there that we can't see yet and so we have to wait for those cases to get sick."
It has also been confirmed the new community cases have the more contagious UK variant of the virus, which Baker said could make matters worse if the second option proves to be the scenario New Zealand is currently facing.
"We know this is more infectious and in the UK it's also been linked to higher rates of hospitalisation and death at the moment.
"This family would be the tip of the iceberg ... so the Government is doing exactly the right thing in treating this very seriously with a short, sharp, intense lockdown to dampen down any transmission until we know more about the sources of this outbreak."