A leading epidemiologist says the best way to prevent future outbreaks of COVID-19 in New Zealand is to prevent the virus from arriving on our shores in the first place.
Michael Baker of the University of Otago wants the Government to introduce a traffic light system, with added pre-departure quarantine and negative tests for countries given a red light.
"The single most important measure for New Zealand is to introduce a way of reducing the number of infected people arriving back into the country," Dr Baker told Newshub Nation on Saturday.
"One approach would be a traffic light system, where we put much more effort into what you could say is the red zone - countries where there is uncontrolled transmission. One option would be to have an additional step before people get on flights from those countries to reduce the risk of them being infected - that could include a brief period of quarantine and a negative test."
Pre-departure testing was considered by the Ministry of Health earlier this year, but Director-General of Health Ashley Bloomfield decided against it, saying the managed isolation and quarantine (MIQ) system "is working".
"[A pre-departure test] has to happen a few days before departure, especially if it's a PCR test, to get a result before they embark," he said in October. "And now what we've got is clearly a number of positive results here at day three that were negative on pre-departure testing...
"The regime we have with our 14 days in managed isolation plus our day three and day 12 testing continues to be the mainstay of how we will keep the virus out of New Zealand."
National promised to introduce pre-departure tests for Kiwis coming home, but lost the election. It remains their policy, new deputy leader Shane Reti told Newshub Nation.
"It just makes sense. It seems like it's only the Government that is saying no, and every other expert in the community is saying yes."
Dr Baker says we're seeing a leak through the border on average once every two weeks. This week's case of community transmission sparked fears of a return to lockdown in Auckland, but on Friday was traced genomically back to a known cluster.
"I think it's a real tribute to the science involved here and the very effective contact tracing systems we have in New Zealand," said Dr Baker. "The genome sequencing has been done very swiftly and effectively, and it's established a link we wouldn't have been able to do previously."
But we're not in the clear yet, he says, because there's still no known physical link between the woman who tested positive and the previously known cases. Any contact between the two is likely to have been fleeting at best - yet some infected people have failed to pass the virus onto others despite close, prolonged contact.
"That is the very erratic nature of transmission," said Dr Baker. "A transmission event depends so much on how infectious the source case is at that particular moment, how close the contact was, how susceptible the other contacts were at that point.
"We know... only about 20 percent of cases are responsible for about 80 percent of the transmission events. That's why on a good day you can be lucky and you won't have an outbreak like this progressing, and on a bad day you can get a super-spreading event where many people are infected."
He's urging everyone to don masks in public, particularly in Auckland, welcoming Cabinet's consideration of making it mandatory on public transport in the city, and on planes nationwide.
"I think while the threat continues, I think yes, it makes huge sense on public transport and aircraft... I think we do need to keep our guard up until we've brought the pandemic under control, at least at a regional level."
Dr Baker has long argued for greater use of masks, even when the World Health Organisation was still sitting on the fence.
Dr Reti said he backs mandatory mask use in Auckland, and nationwide too - but only if the evidence supports it.
Pilots back mandatory masks
Pilots are thrilled face masks might become mandatory following a community COVID-19 case in Auckland.
Air Line Pilots Association President Andrew Ridling told Newshub they have been advocating for this since March.
"The wearing of masks and the use of sanitary wipes on board aircraft should be mandatory until we've got control of COVID or we're gone from this pandemic."