Health authorities have assured New Zealanders there is no rationing of testing for the Covid-19 coronavirus, with capacity to test hundreds of patients a day.

Watch the latest update from the Health Ministry here:

In the latest update this afternoon, Director-General of Health Ashley Bloomfield said there was still just the one confirmed case of Covid-19 in New Zealand.

Dr Bloomfield said there had been 155 tests carried out, with just one returning a positive result, and there were 31 tests under way.

He said one of the two tests he had mentioned yesterday had come back negative. Later this afternoon the second case also returned as negative.

"We still assess our likelihood of a widespread community outbreak is low," Dr Bloomfield said.

Photo: AFP

He said all the testing of New Zealanders for Covid-19 were being done in New Zealand.

He said information was being collected at the border from those people coming from places of concern, including South Korea and northern Italy.

"We are particularly concerned about Iran ... and anyone who came in from Iran in the last 14 days we are strongly suggesting they go into isolation."

He said New Zealand would also be upping the presence of health staff at the border, not to do screening but to improve the information being offered.

Photo: RNZ / Liu Chen

Healthline had more than 1600 calls yesterday, the biggest volume it has faced so far, Dr Bloomfield said.

He pleaded with people to be patient and judicious in their calling to make sure that the people who needed to access it could do so. He advised people making travel plans to use the Safetravel website.

"This is a trust arrangement, but ... everybody here is very clear that self-isolation is an expectation."

Dr Michelle Balm, clinical leader for infection services at Capital & Coast DHB, said while they had been asked about possible rationing of testing, there was capacity to test more than 500 patients a day through ESR and several large laboratories.

"There is easily the capacity for testing and this can also be ramped up over the next few weeks."

Dr Balm said if people were worried they were infected, they should not front up at an emergency department or a primary care provider, and should call the healthline instead.

"We know that's it's not a good idea to test asymptomatic people on the current evidence available. It is likely to give a false sense of security."

She earlier said DHBs were being advised by the Ministry of Health to only test for Covid-19 if the patient meets the clinical and epidemiological criteria.

The clinical criteria includes a fever, or a history of fever which has been equal to or above 38°C, and an acute respiratory infection, with at least one of the following symptoms: shortness of breath, cough, or sore throat.

They must also have travelled to or from countries of concern within 14 days before the onset of illness, or have come within close contact with a confirmed case of Covid-19 within 14 days before the onset of illness.

The areas of concern are mainland China, Iran, northern Italy or the Republic of Korea.

Dr Balm said the large majority of people turning up at hospital asking to be tested for Covid-19 did not meet those criteria.

"Around three per day present with Covid-19-type symptoms that fall far short of the case definition, and another five per day who have no symptoms and do not meet any of the case definition," she said.

"Our doctors are confident that testing is not appropriate on these occasions."

The opposition has criticised the government's claim there has been "textbook response" to the outbreak, saying there were still questions about screening and the availability of tests.

Health Minister David Clark said decisions about who could get tested were based on clinical assessments, and he was "very confident" it was not a case of rationing.

So far, only one case has been confirmed in New Zealand. The woman had returned from Iran via Bali and was recovering in hospital in Auckland.

Total infections worldwide have topped 90,000, with deaths now over 3100. Nearly all cases and deaths have been in China but the numbers in Iran, Italy and South Korea have continued to grow.

Prime Minister Jacinda Ardern yesterday announced people travelling via Italy and South Korea would have to go into isolation for two weeks upon arrival.

Visitors travelling from mainland China and Iran are barred from entering the country, while citizens and permanent residents from those places are being asked to go into isolation.

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