New Zealanders should wear masks in public indoor places under alert level 2 to stop the spread of the virus in the early stages of infection, Otago University epidemiologist Michael Baker says.
The details of the restrictions at alert level 2 are set to be announced today, ahead of a decision due on Monday on when the move will take place.
Baker told Morning Report that New Zealand and Taiwan had taken very similar paths in suppressing the virus.
The only significant difference was over wearing masks.
Taiwan has gone for 25 days without a single local case, has recorded fewer than 500 cases and just six deaths from Covid-19 after early intervention.
"They require masks in certain public enclosed places like public transport in particular," Baker said.
• Covid19.govt.nz: The Government's official Covid-19 advisory website
"It's encouraged but optional in other places. Many shops would require wearing masks and some schools do, but it's not universal."
Baker said the Ministry of Health should front-foot a "mass masking" scheme, which would help stop any further breakouts and give people confidence to use services like public transport.
"The problem with this virus is you may be infected for two, two-and-a-half days before you get symptoms and this appears to be the main way the virus is transmitted.
"And it's not everywhere - it's basically indoor environments."
This was the last risk New Zealand hadn't yet managed, he said, and a simple "mass masking" policy would close off that way of spreading Covid-19.
These could be fabric masks, not necessarily a bought one, and even just a scarf, though not quite as good, would do the job.
"There are a lot of entrepreneurial companies now producing even quite fashionable masks, I have to say, that a lot of people are wearing."
'This is one of the really difficult times for NZ'
In terms of the data, Baker said, it would be good to have a longer period of no cases before dropping down a level.
"We're seeing the effects of the lockdown, which suppresses transmission of all infectious diseases that are spread between people.
"A longer period in level 3 would allow us to see whether we were going to get more cases and outbreaks.
There was also a danger that many people would interpret level 2 as business as usual.
"This is one of the really difficult times for New Zealand.
"We're coming out of this really intense lockdown and in a way complacency is a huge potential problem at the moment."
Overall most of the policies have been really good and have brought down the level of infection.
"But there will be circulating virus, it's highly likely, so outbreaks are a possibility."
Today's briefing is set to spell out what commuters can expect in coming months.