One of the eight patients confirmed today as infected with coronavirus arrived in the country after Monday's travel restrictions were imposed.

The woman, aged in her 40s and currently in Canterbury, arrived on Monday from London, the Ministry of Health said.

The seven other new patients arrived from Europe, Sydney, Gold Coast, and North America - there are now 20 total confirmed cases in New Zealand.

The eight new cases today include four in Auckland, two in Waikato and one in Christchurch and Invercargill.

The Christchurch woman arrived in New Zealand on Monday, after the Government's tough restrictions on travellers kicked in from 1am. Every person arriving in the country, with the exception of those from the Pacific, must self-isolate for 14 days.

The ministry publicly released the patients' flight details this afternoon.

Case number 13: Auckland, male, aged in 50s. Extensive travel through Europe - flight numbers to come.

Case number 14: Auckland, female, aged in 40s. Arrived in Auckland on Monday 9 March from Europe - flight numbers to come.

Case number 15: Auckland, male, aged in 60s. Arrived in Auckland on Friday 13 March from San Francisco on Air New Zealand flight NZ007.

Case number 16: Auckland, male, aged in 60s. Arrived on Thursday 12 March from Canada - flight numbers to come.

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Case number 17: Invercargill, male, aged in 40s. Arrived on Thursday 5 March from the Gold Coast - flight numbers to come.

Case number 18: Canterbury, female, aged in 40s. Arrived on Monday 16 March from London - flight numbers to come.

Case number 19: Waikato, female, aged in 20s. Arrived on Sunday 8 March from Sydney - flight numbers to come.

Case number 20: Waikato, female, aged in 70s. Arrived on Sunday 15 March from Europe - flight numbers to come.

New Zealand had 20 confirmed cases of Covid-19 - an increase of eight from Tuesday - the Ministry of Health confirmed on Wednesday afternoon.

Foreign Affairs Minister Winston Peters told 80,000 Kiwis travelling overseas to get home now - before it's too late.

"If you're travelling it's very likely you could be shut off very shortly," Peters said. "If you can get home, come home now."

Elsewhere, Prime Minister Jacinda Ardern asked every Kiwi who returned to New Zealand in the last fortnight to self-isolate, even if they came back before strict travel restrictions came into force.

She also issued a stern caution about a possible outbreak of Covid-19, saying Kiwis need to plan for scenarios such as working from home and to cancel all non-essential travel.

"This is not a time for panic. It is a time for preparation. I ask everyone that they think about that for them and their family," Ardern told reporters this afternoon.

The Government's plan to contain the spread of the virus seemed to be working so far, but Ardern said there will be more cases and New Zealanders needed to be prepared for a wider outbreak.

"Think about Covid-19 in the same way you do for civil defence emergencies. Prepare a plan for you and your family."

That included thinking about how to work from home, or how to get through a period of self-isolation, including how to access all the resources you might need.

She welcomed Australia adding New Zealanders to its "do not travel" list, noting the travel advice for New Zealanders was similar.

"We have simply given the advice for Kiwis not to travel. Get rid of all non-essential travel.

"There's very few reasons I would have thought anyone would consider travelling at this point."