The "long tail" of Auckland's COVID-19 cluster was to be expected because restrictions aren't as severe now as they were during the first outbreak, New Zealand's top disease modelling expert says.
Shaun Hendy of research centre Te Pūnaha Matatini warns the city's level 2.5 restrictions this time around could cause case numbers to rise, but is hopeful they will instead fall to zero - albeit slower than they would've at level 4.
New Zealand is technically at alert level 2, but Aucklanders have been asked to take extra precautions like limiting social gatherings to groups of 10 and wearing masks on public transport. The Prime Minister has colloquially dubbed this 'alert level 2.5'.
But even with these added restrictions, level 2.5 is a major departure from the severe level 4 restrictions adopted during New Zealand's first coronavirus outbreak - when Kiwis remained in household bubbles, travel was local-only, and all non-essential businesses closed.
Hendy believes the eased restrictions at level 2.5 explain why the Auckland cluster seems to be sticking around for a while longer than last time.
"We did expect quite a long tail to this outbreak," he said.
"What we saw in March and April, we went much harder with level 4, which is much more restrictive on people's movements and what they can do, and that brings case numbers down faster.
"We went for level 3 followed by level 2.5, and that just means we will see these case numbers stretched out a little further and hopefully slowly diminish. But there is still the possibility that we could see them rising again."
The long tail of the current outbreak is consistent with Te Pūnaha Matatini modelling, which showed that COVID-19 would take longer to eliminate this time around because the lockdown isn't as strict.
Hendy worries that with all the activities allowed at level 2.5, Aucklanders may become too complacent too early - putting themselves and others at increased risk of infection.
"Some of the infections we're seeing come from activities that happened under alert level 3. That's just going to take us longer for our contact tracers to trace these cases and put people in isolation," he said.
"We shouldn't be participating in social events with more than 10 people - that's really crucial. If you go out with a couple-dozen people, one of those people could potentially infect that whole group. That's the sort of thing that'll see our numbers spike up again.
"It's really important we take care not to over-socialise - not to go to a party, not to go to church. If we are in a situation where we're in contact with other people - especially indoors - then wear a mask."
Te Pūnaha Matatini is still carrying out modelling work to identify the source of the Auckland cluster, but Hendy admits the research centre is quickly running out of lines of evidence to pursue.
"Unfortunately a lot of the leads we had early on have dried up, and the genomic [sequencing] hasn't given us a clear answer," he said. "It might be one of those things we don't get to the bottom of."
Even still, the Ministry of Health's commitment to a high testing rate over recent weeks has put Hendy at ease that there's no other clusters lurking in the community that we're unaware of.
"I think that shows people in Auckland are taking it quite seriously," he said.
"At this stage, because of the high rates of testing, we're pretty sure that there aren't other cases out there that have been sparked by whatever the origin was - so it's more of a puzzle than something alarming."