New Zealand has recorded another 53 coronavirus infections

New Zealand has recorded 53 new COVID-19 cases, down from 83 the previous day.

Monday's result is the first time case numbers have fallen since the outbreak was identified on 17 August.

But the drop in positive tests correlates with a fall in overall tests.

On Sunday, more than 23,000 tests were reported, but on Monday, health officials reported 16,000.

The new cases identified in Monday's update were all from Auckland. The outbreak tally is 562, with 547 in Auckland and 15 in Wellington.

There are 37 cases in hospital, including five in a stable condition in intensive care.

The new case numbers are being discussed by NZ's cabinet as Jacinda Ardern's government mulls new restrictions.

The prime minister has already flagged the likely outcome.

Auckland, the centre of the outbreak, and Northland, which has had no cases but is linked to NZ's biggest city, is likely to stay at a tough level four lockdown for another fortnight.

The rest of the country, including Wellington and South Island, with no cases, will move to a slightly less restrictive level three lockdown.

Level three keeps limits on almost all social gatherings, but allows for more businesses to open, including cafes and restaurants to open for takeaway.

Experts have called for the alert level system to be refined given the high infectiousness of the Delta variant.

"Our alert level system is quite out of date as it was developed at the start of the pandemic," University of Otago epidemiologist Michael Baker told Radio NZ.

"It did a wonderful job to this point but knowledge has moved on hugely."

Ms Ardern has foreshadowed a tightening of social distancing rules at businesses, should there be further spread of the virus in workplaces.

University of Auckland microbiologist Siouxsie Wiles said the government should tweak restrictions to reduce the "R" value: the number of people every COVID-positive Kiwi infects.

"It's really clear the outbreak is large and likely to get much larger," she said.

"We're seeing a large number of hospitalisations so this may end up being a very serious outbreak indeed.

"We're trying to get this R number of the outbreak below one. If it's below one it means we get the outbreak under control.

"The lower we get it under one, the quicker we'll get it under control."