New Zealand should be ready to move alert levels if there is an outbreak of the new Covid-19 South African variant, a leading modeller of the pandemic says.
Auckland University professor Shaun Hendy said more data on the Northland community case was expected soon.
He compared the Northland community case with the Auckland August cluster but said the new Covid variants were more transmissible meaning if an infected person could infect two more last year, this year they might infect three.
There was accumulating evidence that the new variant spread far more easily, he said.
On 12 August 2020, Auckland moved to alert level 3, while the rest of the country moved to level 2.
"That just means the sort of restrictions we used last year in August in Auckland wouldn't be as effective in containing the outbreak."
However, Hendy said with this case it was "highly unlikely" the country would need to move alert levels the same way; partly because the source of last year's transmission was not identified.
The positive case of the Northland woman can be traced back to the MIQ facility.
"The chances of there being a large number of cases at this stage that we don't know about or that we're unable to track are quite slim."
He said it was not inevitable that there would be leaks at the border.
"We need to be prepared for another Auckland August situation."
Hendy suggested another test five days after a person left an MIQ facility.
"I think it is important to stop people early in their stay in MIQ mixing or interacting with people who are late in their stay. That's a logistical problem."
There was a risk that the virus could be transmitted through the airconditioning system, he said.
So having people stay in their rooms for the entire quarantine period was not a "perfect recipe" to curb infections.
He assumes there will be more information available on any new cases within the next few days.
University of Otago virologist Jemma Geoghegan said research suggested the South African variant could be up to 50 percent more transmissible.
She reiterated what Hendy said, it could mean infecting up to two or three people.
"...which doesn't sound much but when you have exponential growth, it is very concerning."
Geoghegan said the mutation might also be "better at evading antibodies from people that have recovered from that first wave in South Africa".
"Early evidence suggests that some of the viruses that have this mutation might be better at reinfecting people that have recovered or even vaccinated."
She said it was not clear if the vaccines would be as effective on the new variants because they were created on genetic sequence from about a year ago.
There was no information to suggest the variants caused any further severe illness than before the mutation, she said.
But because it was more transmissible, more people could be infected, meaning "proportionally there could be more people in hospital, unfortunately, who die".
She said there were now about 20 countries that have reported to have a case of the South African variant.
Australia suspended quarantine-free travel for New Zealanders for at least 72 hours after confirmation yesterday New Zealand has a case of the South African variant of Covid-19.
PM Jacinda Ardern said she advised her Australian counterpart Scott Morrison that this country had confidence in its systems and processes.
However, she said it was Australia's decision as to how they managed their borders.