A professor of public health has reassured New Zealanders they should go about their "business as usual" after the first confirmed case of coronavirus, and that the risk of contraction is low.

Last night and this morning shoppers descended on supermarkets to stock up after news of the first confirmed case of coronavirus on New Zealand soil.

A person in their 60s is in isolation at Auckland City Hospital after returning from Iran.

But University of Otago professor of public health Michael Baker said there was no evidence of silent transmission, which means others have been infected but it has not yet shown up.

If there was silent transmission, "you'd have seen some evidence by now", Baker said.

"Australia and NZ have been fortunate and planned very carefully for this."

How the case was dealt with was actually "a really nice example of how the [Kiwi health] system is responding" to the world health emergency.

The infectious disease expert said even people who were on the same Emirates EK450 flight as the infected person should not be overly worried.

The flight arrived from Tehran, via Bali, into Auckland on Wednesday.

"They shouldn't be particularly concerned. It doesn't get transmitted completely throughout the airplane environment. It depends on what symptoms were on the flight," Baker said.

He added that probably the only ones who needed to be worried were those near the confirmed case on the plane.

Baker said New Zealand was "still a long way off social distancing measures" of its citizens, after the first confirmed case.

But he ended on a more concerning note.

"Eventually we will see widespread transmission in NZ," Baker said, qualifying the important thing was how it was managed by health authorities.

In a statement, the Ministry of Health said the person in their 60s was alerted to health authorities after their family became concerned about their condition and called Healthline.

"They were advised to seek medical attention and attended Auckland City Hospital emergency department that same day. All were wearing masks on arrival. As a result of the individual's symptoms and travel history they were admitted and tested."

The results of the test were confirmed at 4.15pm yesterday and makes New Zealand the 48th country to have a confirmed case of the virus.

The person is in a stable condition.

"They are in an improving condition in isolation, in a negative pressure room to prevent any spread of the disease," the spokesman said.

In a press conference last night, Health Minister David Clark said the person in their 60s had tested negative for coronavirus twice previously.

The first two tests were negative because they were from a throat sample. The symptoms of a lung infection were present though, so a third test performed.