Covid 19 coronavirus Delta outbreak: Auckland lockdown could last 'three to four weeks', expert says

University of Auckland Covid-19 modeller Shaun Hendy has warned a longer lockdown could be on the cards for Auckland.

Hendy told Newstalk ZB's Heather du Plessis-Allan the reproductive value is very likely under one, which means over time we will bring this outbreak under control.

Hendy told du Plessis-Allan how long that will take is the "million-dollar question".

University of Auckland Covid-19 modeller Shaun Hendy says Auckland may face a few more weeks in lockdown. Photo / Dean Purcell

"Two weeks is probably looking a bit tight, but it's not impossible at this stage," Hendy said.

"It's possible we could see a shift out of level 4 in two weeks' time, more likely something like three to four weeks."

Earlier on Thursday, the Government announced 49 new Covid-19 cases but Prime Minister Jacinda Ardern said that only seven of these were infectious while in the community.

Compared to previous lockdowns, Hendy said in this lockdown testing levels have gone up and there's a better understanding of where the virus is spreading.

"I think this outbreak is different in that it has impacted our essential workforce more and that explains some of these cases."

Hendy said current cases show more needs to be done to ensure essential workers are working in safe environments and monitor their health.

"We don't want people to be infectious in the community, particularly when they are working, it's so important that people monitor symptoms and get a test," he said.

Earlier on Thursday, director general of health Ashley Bloomfield said essential workers in Auckland, in particular, had to stay home if they were contacts or had been to a location of interest.

Compared to last year's lockdown, Hendy doesn't believe the Government will wait for two weeks of zero community cases to move alert levels.

"We will have the confidence to move a little bit sooner into alert level 3 but there is a lot of time between then and now and a lot could still go wrong," he said.