The latest Covid-19 case in Northland is the country's first in the community of the new variants sweeping the globe.
Covid-19 Response Minister Chris Hipkins today confirmed the case was the South African variant, which is believed to be more infectious than the original strain of coronavirus.
It was "highly likely" the woman, aged 56 and who lives south of Whangārei, had contracted the virus from a fellow returnee during her stay in managed isolation in the Pullman Hotel in Auckland, between January 9-13.
"This is good news because it means we know where the source of infection is and we don't have to divert our scientists and health experts from other Covid-related work," Hipkins said.
Director-general of health Dr Ashley Bloomfield said there was little epidemiological data available to date about the South African variant, called B.220.127.116.11.
"What we know so far is that it may be more transmissible, but that's not as clear as the information about the variant first identified in the UK.
"There is some evidence that this variant may evade some aspects of the body's immune response."
Bloomfield said it was still early days and they would keep a watchful eye on what this means.
New forms or variants have become "increasingly common" around the world.
"They are not confined to specific countries. And we had expected to see them in New Zealand."
Another variant called B.1.1.7 has spread very quickly within the UK, and while one other variant has also been observed in Brazil.
As of January 21 the Ministry had detected 36 people arriving in New Zealand with the contagious strains since they emerged late last year - 29 samples of the UK variant and seven of the South African variant.
The Herald has sought more up-to-date data but did not receive a response by time of publication.
The variants have emerged through changes in the genetic code of Covid-19, as occurs in other viruses all the time, but most mutations don't have any effect on how the disease spreads or its severity.
But the new variant detected in the UK is more transmissible than the original virus that was dominant in 2020. That means it spreads more easily from one person to another.
New data has also found it to be more deadly.
Professor Neil Ferguson, of the British Government's virus advisory committee, said the latest data showed up to 13 in 1000 people aged 60 who contract the variant strain could die, compared with 10 in 1000 who caught the original variant.
The variants found in South Africa and Brazil share some of the same mutations as the B.1.1.7 variant. There is some evidence they may also be more transmissible or better able to evade immunity.
But there is more uncertainty about these variants, partly because the data quality isn't as high as in the UK, which is very good at doing genome sequencing.
With the UK variant, the average number of people an infected person with Covid-19 passes the virus on to — the so-called R number — is 40-70 per cent higher with B.1.1.7 than the original variant.
This means because of exponential growth, a 50 per cent increase in transmissibility causes 25 times more cases in just a couple of months if left unchecked, according to modelling by Professor Michael Plank of the University of Canterbury and Professor Shaun Hendy of the University of Auckland.
That would lead to 25 times more deaths at the original mortality rate, and even more if the rate is higher.
Plank and Hendy say this higher rate of infection for the new variants mean any community outbreak needs to be matched with greater tools.
For example, in the Auckland outbreak in August 2020, alert level 3 was enough to contain and eventually eliminate the outbreak. Our analysis showed alert level 3 reduced R to about 0.7.
"If we had a similar outbreak with the new variant, R could be 50 per cent higher which would mean it is above 1.
"In other words, we would likely need to use alert level 4 to contain an outbreak, and it might take longer to eliminate the virus than it has previously.
"To give our contact tracers the best possible chance of containing a new outbreak without needing alert level 3 or 4, we all need do our bit.
"This means looking for QR codes when out about and using the app to scan them, as well as and staying at home and getting tested if you feel sick."