COVID-19: What needs to happen for Auckland's level 3 lockdown to end at midnight Friday

Dr Siouxsie Wiles has revealed the four key things that need to be done to ensure Auckland's COVID-19 alert level 3 lockdown isn't extended past midnight Friday.

Prime Minister Jacinda Ardern and Director-General of Health Dr Ashley Bloomfield announced four new cases of community transmission on Tuesday night, New Zealand's first in 102 days.

As a precaution, Auckland was placed in alert level 3 and the rest of New Zealand into alert level 2 from midday Wednesday.

The Prime Minister said the lockdown will last for three days, until midnight Friday, but may be extended if the risk of COVID-19 is still significant.

University of Auckland microbiologist Dr Wiles has now revealed the four things she believes need to be done in order for the lockdown to finish by Saturday.

"[It will] really depend on where the [family who tested positive] picked up the virus," Dr Wiles told Newshub.

"So if it looks like there is a missing link in the chain then this is going to mean a bit more work to try and find out whether there are missing cases and stuff like that."

The three other factors are: "whether all of the contacts have been traced and are isolated and whether any of them are infected," Dr Wiles said.

"Then [we need to know] whether anyone they know has been isolated.

"We also need to have done a huge amount of testing around Auckland and testing symptomatic people around the country and making sure none of those come back positive."

Dr Wiles said New Zealanders recording their movements is key.

"It depends on if people remember where they have been and whether they have been keeping track of all of that and whether the Ministry of Health has people's contact details," she said.

"We have been asking for weeks for people to use the app or to keep track of where they have been and who they have been with. Just downloading the app and filling in your details so the Ministry of health has your updated contact details is really important."

But she is warning New Zealanders: "I think it is probably more likely to be extended to be honest. Or at least I think we should be preparing ourselves for that."

University of Otago professor of public health Michael Baker said he believes the lockdown will end when the Ministry of Health is confident the community spread of coronavirus is under control.

"They basically have to feel confident that the new source of the outbreak and how many cases in the community that they have identified all of them, they were safely put in managed isolation or quarantine and that it is fully under control," he said.

"You hope that… all of the contacts that are identified haven't, in turn, infected lots of people. So that's the hope, that the outbreak is small and well defined and we are not left with any doubts by Friday as to where it came from and who else might be infected. That's the ideal."

But Prof Baker said even if the lockdown does end at midnight on Friday, New Zealanders should still expect some restrictions to continue.

He is urging Aucklanders to download the COVID-19 Tracer App and follow the lockdown rules.

"The most important is if you have symptoms is to stay at home, away from other people and get tested. That's really vital," he said.

"The second thing is minimising the risk of infecting other people. That means obviously washing hands and wearing a mask or face covering...

"People of Auckland should not go to large social gatherings, particularly informal ones... just have a quiet time at home for the next couple of weeks and don't have social events."

Dr Wiles agreed and urged anyone displaying symptoms of COVID-19 to call Healthline or their GP, or pop into a testing centre and get tested.

"We are at alert level 3 and I'm hearing stories of people trying to disappear off to their baches at coromandel but don't do that, stay home and stay in your bubble."