The unknown source of Auckland's COVID-19 outbreak is a "worry", an expert says, but Cabinet will also have to consider the multimillion-dollar cost of keeping our largest city in lockdown.
Prime Minister Jacinda Ardern's Cabinet meets at 3pm on Wednesday to weigh up the latest data and advice on whether to extend the alert level settings. She will announce the decision at 4:30pm with Director-General of Health Ashley Bloomfield, and you can watch it on Three or Newshub online.
A spokesperson for Ardern said Cabinet wants to ensure it has the most up-to-date information, and going slightly later in the day - rather than the usual 1pm press conference - means being able to oversee all the testing results possible to inform the decision.
And what significant decision it is.
Auckland was put into a three day alert level 3 lockdown starting from Monday after three cases of COVID-19 were discovered in the community - a Papatoetoe High School student and her parents. The mother works at LSG Sky Chefs which does laundry for flights, and it has been flagged as a possible place of transmission.
Contact tracing has identified 109 close contacts. On Tuesday, 33 had returned a negative test and 74 results were pending. More than 2000 contacts have been identified as casual plus - these include people at the parents' workplaces, Papatoetoe High School and other locations.
COVID-19 Response Minister Chris Hipkins confirmed on Wednesday morning that after thousands of tests across New Zealand - 15,000 people were tested on Monday - no additional positive test results had come through.
Hipkins later confirmed to a parliamentary select committee on Wednesday two additional cases connected to the family. Both are students at Papatoetoe High School.
The low numbers of cases could give Cabinet the confidence to avoid the enormous expense of extending the lockdown. Economists estimate that each day Auckland is under alert level 3 costs about $45 million, and a 40 percent daily drop in consumer spending.
But Cabinet will also have to consider the cost of lifting restrictions too soon.
"It's about whether we want to yo-yo in and out," microbiologist Dr Siouxsie Wiles told The AM Show. "My advice would be we stay a couple of days and see what happens. The last thing I think we all want is to come back out of alert level 3 and then need to go back into it again next week."
Dr Wiles is concerned about what we don't know - the source of the outbreak.
"We have to remember that the virus has an incubation period usually around two to 10 days for most people but some people can be about 14 which is why we have this 14 days in managed isolation and quarantine," she said.
"The test that people have is a point-in-time test, so that time when they were tested and they were negative is great, but there are close contacts that could still be within those 14 days and could test positive in a few days' time."
Dr Wiles said it's important to remember that just because there were negatives doesn't mean they might not become positives in a few days' time, and on top of that the source is not yet known leaving lots of question marks.
"It is a worry not knowing the source, that's why the wide net's been cast. What we're concerned about is that there might be some transmission chains that we haven't identified yet. The other thing about this virus that's very frustrating is that not everybody infects somebody else."
Why hasn't the outbreak spread?
Genome testing revealed early on that the family had contracted the UK variant of COVID-19 which scientists say is much more contagious. And yet so far, it hasn't spread far beyond the student and her parents.
This could be explained by the 80-20 rule.
"With this virus, about 80 percent of infections are caused by 20 percent of people. Some people don't go on to infect anybody or only infect one person and then you have other people involved in these super-spreader events where you can end up with tens or hundreds of people infected," Dr Wiles said.
"That's the worry, that if there are some people out there that aren't detected, once we move back to alert level 1 and we're all meeting at large gatherings and things, there's that potential for a super-spreading event."
Haven't we been here before?
There have been seven community outbreaks of COVID-19 in New Zealand, but only three have sparked lockdowns. The first major one was in March last year when we all went into alert level 4. The second one, in August, is reminiscent of the current outbreak - but there's one big difference.
"With this one we've done extensive testing, as we did in August, and it hasn't thrown up any additional cases thus far. That's really encouraging," Hipkins said on Wednesday morning. "But there are a few other things Cabinet will look at - what more we know about the potential source, and so on."
Hipkins said the latest outbreak is "quite different" from the August experience.
"You may remember we did a 72 hour lockdown because we saw an undetected case in the community, we didn't know where it had come from, we then saw in the days immediately afterwards a number of additional cases and that grew exponentially and we ended up dealing with well over 100 cases in that August outbreak."
But just because only a few new cases have emerged doesn't mean there isn't risk of a larger outbreak, because the source remains a mystery - as it does with the August outbreak.
"The thing about this particular case is all of our potential sources are looking like they're highly unlikely. Could it have come off the laundry? Highly unlikely but possible. Could the daughter have picked it up somewhere in the community? Highly unlikely but possible. That's what this investigation process looks at," Hipkins said.
"We may never be able to nail it down but what we can do with the extensive testing that we've been doing, the contact tracing we've been doing, is really minimise any risk of further spread, and that's looking pretty good so far."