Coronavirus: Prime Minister Jacinda Ardern's stark warning ahead of COVID-19 lockdown

The Prime Minister has issued a stark coronavirus warning: "Expect our numbers to keep rising, because they will".

Jacinda Ardern was speaking to media on Wednesday, just a few hours out from New Zealand heading into lockdown to combat the spread of COVID-19.

She said the numbers will look bad before the lockdown measures kick in and start to have a noticeable effect.

"Modelling suggests we could have several thousands of cases before we see the impact of what we're doing today," she said.

Director-General of Health Dr Ashley Bloomfield reiterated New Zealand would continue to see a rise in cases for at least 10 days.

That includes cases like those of Joshua Dent, who is now recovering from the new and unknown virus.

"[I'm] just extremely lethargic and fatigued - [I've] managed to tick off every symptom under the COVID-19 umbrella," he said.

Dent is in strict isolation at his Northland home since he got back from London 10 days ago.

"I got a little bit worse there in the middle; that scared my family a little bit, and myself," he said.

Dent is among the 205 cases now confirmed in New Zealand - 73 of which are in Auckland, where four were community transmission.

The capital has 32 cases and the Waikato, Canterbury, and Dunedin have about a dozen each.  The rest spread far and wide throughout New Zealand.

Six of the sickest are being treated in hospitals around the country.  

"None are in [the] intensive care unit," Dr Bloomfield told reporters on Wednesday.

Of concern will be the mystery cases that pop up in that time that can't be traced. Research director Shaun Hendy is crunching the numbers on our outbreak.

"The thing we're watching carefully is community transmission cases," he said.

"There's a number of scenarios - best-case, we are maybe able to stamp it out in the next four weeks and then we can keep the number of deaths to a very small number."

But the worry is if the virus gets out of control in New Zealand, as it has overseas. Already two clusters of concern have been found - one from the Hereford Cattle Conference, and another at an all-girls school.

"We now have five confirmed cases in the community in one school - the Marist College in Auckland," Dr Bloomfield said.