New Zealand may be "close" to eliminating Covid-19 transmission but more detailed information is needed to be sure, epidemiologist Michael Baker says.
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Nineteen new cases were added to the country's tally yesterday, meaning a total of 1349 cases since the pandemic was first identified in New Zealand.
Epidemiologist Michael Baker said the missing knowledge was how many of those are infected people who are in quarantine at the border.
Baker told Morning Report some conditions for moving out of level 4 lockdown were in place but the surveillance system needed more work.
" The thing we want to achieve is no transmission in New Zealand" - Michael Baker
New Zealand already had good quarantine at the borders. It was also ramping up the ability to do very rapid outbreak control, which involves a lot of testing, case identification and the ability to rapidly follow up large numbers of contacts and quarantine them, he said.
"The third component is this very good surveillance system to rapidly pick up any cases or outbreaks or clusters when they occur.
"I think that still needs more attention and thought.
"We've got a large volume of testing. We're starting to see this distributed across the country. But I think we do need more information about how that system is working, and its capacity.
Baker said a detailed breakdown of new Covid-19 cases was needed.
"The missing knowledge is what proportion those cases are just people detected at the border and happily quarantined - because they they don't pose a risk to New Zealand - and how many of those cases are actually in the community.
"It's quite hard, without that knowledge, to really have an opinion on where we're at with control.
"The goal is elimination, so that's no transmission in New Zealand. But my understanding is we will still have cases being detected in returning travellers to New Zealand."
Baker said New Zealand was "very close" to that goal.
"When we know are all those systems are operating, when we can see the data on transmission in New Zealand - and there are still some clusters that are being followed up so we just need to know that those numbers have essentially been extinguished - and then I think will will feel a lot closer."
Baker said about half of fatalities in Europe and the UK had been in aged care facilities, so rest homes should be a critical focus. "It's absolutely critical to protect them."
The World Health Organisation is advocating a slow return to business as usual.
Baker said lowering alert levels in New Zealand would take many months of a "carefully worked out graded, return to normal".
"It's going to be quite nuanced because even when we open up schools, again, they will be organised differently to reduce the risk."
There will be no normal movement across borders until there were vaccines, anti-virals and other systems available, which may take more than a year, he said.
A group of New Zealand academics is calling for a significant loosening of restrictions when the lockdown ends.
Auckland University epidemiologist Simon Thornley told Morning Report the group believed the lockdown was an overreaction and did not match the threat posted by the virus.
He said they had not done their own modelling but observed what had happened in other countries with less severe lockdowns such as Australia.
He said most deaths from the virus had occurred in elderly, frail people with underlying health conditions.
"We know that they elderly, unfortunately every flu season people die of seasonal influenza."
There was a high cost to lockdowns, such as in Spain where unemployment had jumped, he said.