New modelling shows the number of people infected in the community might reach 120 - as large as initially feared.
Shaun Hendy at his kitchen table, where he's doing NZ's modelling of Covid-19 Photo: Supplied
Genome sequencing has found the current positive cases are a close match to a recent returnee from Sydney, who arrived on a managed red zone flight on 7 August.
It's a promising link to the border that had Covid-19 modeller Professor Shaun Hendy guessing the number of people infected in the community could be "several dozen", as opposed to up to 120, earlier this afternoon.
This was pending Professor Hendy running more numbers for an updated model, which has since returned figures similar to initial predictions.
"The good news is that that later introduction date means that the virus has been in the community for a shorter period of time. That means we're probably not looking at many other undetected chains of transmission.
"However, when we look at the case numbers that we've found so far, and when those people were likely infected, we had a very, very rapid spread late last week, going into the weekend."
The numbers show some people had been at locations of interest, the number of which is growing by the hour, while infected, he said.
Despite predictions, there may still have been "about 100 cases" in the community at the time the outbreak was first detected, Hendy said.
"We'll be a lot less concerned about there being other chains of transmission out there. That'll help us get put a ring around this particular cluster and should enable our contact tracers to have a better chance to, to contain it."
Although this outlook is optimistic, it was still entirely possible there are undetected Covid-19 cases in parts of the country beyond Auckland, he said.
'It's a game changer'
Public Health expert professor Philip Hill told Checkpoint the match to the recent returned means there is a clear start date.
"It's a game changer because it basically suggests that we have a start date for the outbreak. And instead of the possibility that the virus might have been circulating for several weeks or even over a month, like maybe it did last year at this time, it may well have only been circulating in the community for only a matter of days."
But Hill said there will still be more cases.
The number of infected people has more than doubled over the last 24 hours from 10 to 21, and modeller professor Shaun Hendy expects those numbers to rise to about 120.
Hill said the fact three people staying in managed isolation opposite the Sydney returnee have also returned positive results shows there was a "serious systems failure".
Hill also said there were two major concerns with wastewater testing, which had returned positive results at three Auckland sites earlier this week.
There were doubts about how sensitive the testing was, and how it can't distinguish between an unviable virus and a viable virus, he said.
"In other words, when you're no longer infectious, and you're getting rid of still some viral particles that have parts of the genome still detectable. Then it'll still be positive in the wastewater so as you resolve an outbreak, you'll still have wastewater positive for, you know, sometime after the outbreak is actually cleared or finished."
He said the government had more information about the outbreak than he did, so trusted them to make the call on changing alert levels.
This is an official Covid-19 ALERT.
All of New Zealand is now at Covid-19 alert level 4.
The alert level will be reviewed after 3 days for all areas EXCEPT Auckland & Coromandel Peninsula which is likely to remain at level 4 for an initial period of 7 days.
A community case of Covid-19 has been identified.
Stay at home where possible & follow the Alert Level 4 guidelines. This will stop the spread of Covid-19 and SAVE LIVES.
Everyone is asked to:
Wear a mask and keep a 2 metre distance from others whenever you leave your home.
If you are sick, call your doctor or Healthline on 0800 358 5453 for advice about getting tested.
Keep on scanning QR codes whenever you leave your home.
Practice good hygiene - wash hands often.
Services including supermarkets, pharmacies, clinics & petrol stations will stay open at Alert Level 4. Face coverings are mandatory for all people - both employees and customers - at businesses and services operating at Alert Level 4 involving customer contact.
For more information on Alert Level 4 go to [the government website www.covid19.govt.nz]
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Kia Kaha - Stay Strong
