Kiwis are being told they'll need to get used to wearing masks in their everyday lives if we're going to prevent COVID-19 getting a foothold here.
The first four cases of community transmission in more than 100 days were reported on Tuesday night, Auckland jumping to alert level 3 the next day and the rest of the country level 2.
Masks are not yet mandatory, but the Government is investigating its legal options, particularly for Auckland.
"When people cannot maintain physical distancing of more than two metres, such as on public transport, at work places or in shops, face masks will be particularly important," the Ministry of Health's website reads.
Royal New Zealand College of General Practitioners medical director Bryan Betty told The AM Show on Thursday the evidence they can stop transmission of the SARS-CoV-2 virus is now beyond doubt.
"At the start of the year... there was a lot of confusion about masks - did they help or didn't' they help? What's become really obvious over the last few months, and from the experience around the world especially in Asia, countries that wear masks in public places - such as public transport, where there's big gatherings - reduce the transmission of COVID. There's no doubt about this now."
Masks have been common in many Asian countries in recent decades, having been through the original SARS epidemic in 2002/3 and suffering heavy air pollution thanks to rapid industrialisation and a lack of environmental regulations.
"I think it might take a bit of getting used to for New Zealanders because we're not used to doing it in public, but there's a real positive to actually doing it and disrupting the transmission of COVID," said Dr Betty.
While masks can help prevent contracting the virus, they're arguably even better at stopping you passing it on, should you be infected without knowing it. The virus' primary form of transmission is via droplets, so anything you have over your mouth and nose will help.
A crude but effective meme doing the rounds on social media explains how - if you're wearing jeans and someone pees on you, your legs only get a little bit wet; but if they're wearing jeans, you don't get wet at all.
"Masks are excellent for source control, ie. not passing infection to others - not so much for prevention of 'getting' diseases, hence masks should be on whenever people are out and about," said Arindam Basu, an associate professor of health at the University of Canterbury's College of Education.
"Any mask is good, except for those with valves on them. The clue is to wear them properly covering nose, and take care not to overlap with glasses to avoid fogging."
Dr Betty says in a pinch, virtually anything that prevents droplets escaping will do.
"If you don't have a mask, then quite honestly a scarf across the face or even a bandana will have some sort of protective effect. It's slightly inconvenient, it doesn't look that great, but at the end of the day it's about safety, it's about reducing any transmission that might be out there."
Like Director-General of Health Ashley Bloomfield, Dr Betty says it was always probable there would be another outbreak of COVID-19,which has killed three-quarters of a million people worldwide.
"It's a really stressful, anxiety-provoking time for a lot of New Zealanders. Certainly I think it's tough but you know, at some point this was probably going to happen. It's really unfortunate it's happened now. But we need to get on top of this really, really quickly - and just disrupt the transmission and shut this down. Difficult, hard, hopefully this is short."
He expects the short three-day lockdown to go on, particularly with the confirmation of another case on Thursday morning at Mt Albert Grammar School.
"The next 72 hours is critical. I think you'd put odds that this would possibly be extended and I think we need to be prepared for that... that is the reality we're facing."