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As health officials race to track the the origins of the community outbreak of Covid-19 as the cluster hits 17 cases, disease modeller Shaun Hendy says a lockdown extension is likely.
Since four members of the same Auckland family tested positive, a student at Mount Albert Grammar is confirmed to have the coronavirus, as well as three workers from a cool store, a finance company worker and one of their family members.
There are also seven family members of already infected people. The Director General of Health says all the new positive cases will be moved to managed quarantine facilities.
And all staff working at the borders, including our ports and managed isolation facilities are in the process of being tested.
Prior to this latest outbreak, physics professor and disease modeller Shaun Hendy was calling for all those front line workers to be routinely tested once a week.
"Everything is still linked to the cold store facility, and that's good news in some ways, because we haven't seen other clusters out there in the community.
"It's still a little bit unnerving, in that we still don't know the route of transmission from the border to the cold store facility, and that's actually crucial for us being able to estimate how bad this outbreak might get."
Professor Hendy said the evidence pointed to the virus coming in from the border.
"We were very sure we'd eliminated the virus in New Zealand, so it almost certainly has come somewhere through the border, and I think there have been some indications from the genomics already that we are looking at something that's not closely related to the virus we had earlier in the year.
"It's not this family in particular that it's pointing to. It goes back to that workplace. So I think the strongest possibility is some connection from that workplace to the border in some way. "
The possibility the strain of Covid-19 arrived on an imported product was unlikely, Professor Hendy said, given the evidence.
"There are a few pieces of evidence overseas that do suggest that it can be picked up from from surfaces but what we know overwhelmingly is it is person to person contact that spreads the disease. So that's our most likely scenario."
Testing the products at the cold storage facility is more about ruling out that possibility, he said.
What next for lockdown?
"I think the decision to let us free out of Level 3 in Auckland, that would only be if we had really, really clear evidence of the chain of transmission, and if that was a relatively short chain of transmission.
"That's probably not a likely outcome, we probably won't have clear evidence about that tomorrow, so I do think we're probably looking at an extension of lockdown," Professor Hendy said.
"As the information comes in overnight and during the morning, that will help build a bigger picture, and Cabinet are definitely using that in their decision-making."
It would be the wisest thing to do, to give health experts more time to investigate the links between cases and make sure we understand the contact at the border.
Pushing out the alert level 3 restrictions in Auckland would be helpful, he said, but could be longer if more cases appeared over night before the Friday deadline.
"If we learn overnight and tomorrow that we have identified other clusters, we might be looking at an extension of several weeks."
Professor Hendy's personal preference would be for a harder lockdown over a shorter period of time, but it would be difficult to maintain the borders around Auckland.
For the rest of New Zealand, alert level 2 was effective enough, "given what we know," he said.
"But we should all be cautious, we should assume the virus has travelled outside Auckland."
That meant isolating immediately if you had Covid-19-related symptoms, and getting tested, he said.
How many more cases could there be?
Professor Hendy runs data modelling to estimate how big the Covid-19 spread could be.
"Let me be clear, there are big, big error bars here. It depends a lot on the information that we'll find out in the next 24 hours.
"But the simulations we've been running suggest maybe 30-40 active cases at the moment, with an upper limit of 70-80."
The best case scenario would be if all cases are linked to the south Auckland cold storage cluster, he said.
"There'll be a long period of uncertainty unless we can nail down that direct connection to the border.
"If this turns out to be the only cluster than actually I think we probably got quite lucky."