It is the question on everyone's minds as they wake up to Day three of Alert Level 4 today, will the lockdown be extended?

Prime Minister Jacinda Ardern will announce any alert level changes at 3pm following a meeting with her Cabinet ministers this afternoon.

She has already signalled Auckland and the Coromandel Peninsula will be in alert level 4 for seven days, while the rest of the country has been given a stay-at-home order for at least three days.

Epidemiologist Professor Michael Baker says the government simply won't know enough about the outbreak to ease restrictions today.

"The trouble for the government is that they really won't have enough of that information to make a decision to take the rest of New Zealand out of alert level 4.

"I'm pretty certain that they'd want to wait a few days longer, or perhaps give it a full week, before they might review that decision, simply because they won't have enough knowledge about that."

Michael Baker Photo: RNZ / Samuel Rillstone.

He says it's still unclear if the virus has spread beyond Auckland, but rapid Covid-19 testing and wastewater testing will clarify this picture in the coming days.

It's almost guaranteed Auckland will remain at alert level 4, Baker says.

Auckland Business Chamber chief executive Michael Barnett says a lockdown extension will come as no surprise to the city's businesses.

"I think Auckland having so many of the quarantine hotels made it almost inevitable that there was going to be a community case and I think an acceptance that it would be sometime soon."

Barnett says the government swiftly reinstating its wage subsidy and resurgence support payment schemes has given businesses certainty going into the lockdown.

There are now more than 100 locations of interest.

Yesterday, genome sequencing found the current positive cases are a close match to a recent returnee from Sydney, who arrived on a managed red zone flight on August 7.

It's a promising link to the border that has Covid-19 modeller Professor Shaun Hendy guessing the scale of the outbreak could be much smaller than initially feared.

He anticipates the number of people infected in the community at the time the outbreak was first detected could scale back to "several dozen".

This is pending Hendy running more numbers for an updated model, which has since returned numbers similiar to initial predictions.

"The good news is that that later introduction date means that the virus has been in the community for a shorter period of time. That means we're probably not looking at many other undetected chains of transmission.

"However, when we look at the case numbers that that we've found so far, and when those people were likely infected, we had a very, very rapid spread late last week, going into the weekend."

Hendy says it's unlikely the government will ease alert level 4 restrictions, given the lingering possibility people may have been exposed to the virus and travelled around the country.

"I think we're going to have to wait a while until we can rule out transmission to other parts of the country.

"Certainly down the track if we don't see cases emerge in the South Island it can probably anticipate coming out of alert level 4 earlier, but given the scale of what we're potentially dealing with here in Auckland we do need to be cautious about that approach."

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This is an official Covid-19 ALERT.

All of New Zealand is now at Covid-19 alert level 4.

The alert level will be reviewed after 3 days for all areas EXCEPT Auckland & Coromandel Peninsula which is likely to remain at level 4 for an initial period of 7 days.

A community case of Covid-19 has been identified.

Stay at home where possible & follow the Alert Level 4 guidelines. This will stop the spread of Covid-19 and SAVE LIVES.

Everyone is asked to:

Wear a mask and keep a 2 metre distance from others whenever you leave your home.

If you are sick, call your doctor or Healthline on 0800 358 5453 for advice about getting tested.

Keep on scanning QR codes whenever you leave your home.

Practice good hygiene - wash hands often.

Services including supermarkets, pharmacies, clinics & petrol stations will stay open at Alert Level 4. Face coverings are mandatory for all people - both employees and customers - at businesses and services operating at Alert Level 4 involving customer contact.

For more information on Alert Level 4 go to [the government website www.covid19.govt.nz]