A Covid-19 modeller expects to see the national lockdown have an impact on new case numbers by the end of the week.
A queue at the St Lukes Covid-19 testing centre. Photo: RNZ / Marika Khabazi
University of Canterbury's Dr Michael Plank told Morning Report the 21 new cases reported yesterday, which bumped overall Covid-19 community cases up to 72, were to be expected.
There were 20 more cases in Auckland and one case in Wellington announced by the Ministry of Health, all linked to the existing cluster.
The number of locations of interest continues to rise, with six schools and several gyms and supermarkets on the Ministry of Health's expanding list.
The Samoan Church of God in Auckland is a particular concern for health officials and it has been linked to three cases in Wellington.
Plank expected new case numbers to stay the same during the beginning of the week as more close contacts get tested, unless there were significant super-spreader developments.
"I think it's tracking more or less as we would have expected," he said.
"We'll probably see cases bounce around - that 20 per day mark for a few days yet, although it could go higher if we do see any significant super spreading from those large locations of interest as the test results from those come in."
Plank expected to see numbers start to show signs of decline by near the end of the week, which would suggest the lockdown was having an effect.
"I think it will be into the second half of this week. We know that it takes at least a week because of the incubation period of the virus and so it's probably going to be Thursday or Friday before we start to see the signal of that lockdown come through in the case numbers and then hopefully start to bring those daily case numbers down."
Professor Michael Plank. Photo: Supplied.
Plank said it was encouraging to see no other clusters of cases being identified, but cautioned that didn't mean other clusters weren't out there in the community.
"It's definitely good news that the vast majority of those cases reported have been linked to the same cluster and that's a sign that our contact-tracing system is doing a really good job of tracing people down," he said.
"We're not completely out of the woods yet in terms of another cluster being out there because people could still be in the incubation period and may not come forward for testing for a few more days.
Although the incubation period for the Delta variant can be short, he said there was a wide range of variability in its incubation period, so that it was still possible for people to be incubating the virus or a week or longer.
The fact no cases had been picked up in Coromandel was also fortunate, Plank said.
The index case - a 58-year-old man from Devonport - had visited several locations in Coromandel before being diagnosed with the virus.
"That's definitely a good sign and it's possible that just through luck that they didn't affect anyone while they were there, or just happened to be not quite in the right time window relative to their infectious period. It's obviously important to continue test there."
"It's likely that it will be a least another week" - Professor Michael Plank, Covid-19 modeller
An extension of the alert-level 4 national lockdown was very likely today, followed by extension decisions every week, he said. The government will be announcing its decision on a lockdown extension at 4pm today.
"It certainly needs to be extended and it's likely that it will be a least another week," Plank said.
"I think it makes sense to go week-by-week at this stage because a lot can change within a week and then in another week's time we can have a clearer picture as to how that lockdown is starting to take effect. A week seems a reasonable timeframe for Auckland.
He was cautious about the idea of any regional lockdowns, given how easily the Delta variant can spread and the ineffectual nature of regional lockdowns in Australia. Although regional lockdowns were inevitable, he added.
"At some point it's likely to see different parts of New Zealand at different alert levels, but we do need to remain cautious. We know there are around 150 contacts identified outside of Auckland and Waikato and they're just the ones we know about.
"As I said, people could be still in the incubation period. At some point we are going to see this but we do need to remain cautious and we've seen in New South Wales how easily the virus can spread out into regional areas we you have a big outbreak in a major urban centre."