Epidemiologist Michael Baker is warning the Government not to loosen COVID-19 restrictions in Auckland after a spike in cases on Sunday.
Prime Minister Jacinda Ardern will at 4pm reveal restriction updates for Auckland, Northland and parts of Waikato - all of which are at COVID-19 alert level 3.
Speaking to The AM Show on Monday Baker, from the University of Otago, says the number of people ending up in hospitals with COVID-19 is already a worry. The latest Ministry of Health data shows there are 33 people in hospital with COVID-19, seven of whom are in intensive care.
Baker described Sunday's case spike as an "exponential rise".
"We know, at the moment, we're seeing about 10 percent of cases who are going to hospital - which is actually a very high proportion," Baker said.
He said the Government needed to act accordingly.
"A lot of it comes down to the ability of the health system to manage the numbers," Baker told host Ryan Bridge.
"We have to act early rather than waiting until the system's overwhelmed."
Baker said New Zealand should still look to eliminate COVID-19 but noted it would be harder to do so in Auckland.
"The broad goal is still elimination ideally but in Auckland, we may have to settle for continuing cases for the next couple of months until we can get really high vaccine coverage."
Shaun Hendy, a COVID-19 modeller, said the outbreak was at a crucial stage.
"It is possible that… [cases] could end up in the triple digits so that's something that the Government should be considering, and it should be developing a plan for what happens," he told RNZ.
Hendy said a circuit breaker alert level 4 lockdown might be required if daily COVID-19 cases reach triple-digits - something that's yet to happen in the Delta outbreak.