Eight further cases of the Covid-19 coronavirus have been confirmed in New Zealand, bringing the total to 28, says the Health Ministry.

Director-General of Health Dr Ashley Bloomfield has given the Ministry of Health's latest update on the Covid-19 coronavirus.

Dr Bloomfield said the eight new cases were all linked to overseas travel, meaning the coronavirus has not yet been transmitted in the community.

Two of the new cases are in Southland, two are in Taranaki, one is in Rotorua, one in Northland and two in Auckland.

One of the new Southland cases is in hospital and the rest are at home in self-isolation.

None of the new cases are from the Dunedin school that was shut down and cleaned after a confirmed positive case, or from any other school.

Most of the tests from the Dunedin school have come back negative so far.

Close contacts will be traced and contacted, Dr Bloomfield said. They will be required to take 14 days of self-isolation and those who were on the same flights into the country and sitting within two seats to the front, rear, and side and diagonally will be contacted.

"We are expecting more given the rapidly evolving situation overseas and the number of people who have returned to New Zealand, if they are Kiwis or if they have come from other countries, from some of those hotspots."

For those who have travelled back from overseas and are asymptomatic, social distancing and self-isolation are important, Dr Bloomfield said.

Dr Bloomfield said it was important to look after our individual and collective wellbeing, not just physical but mental too.

He said a psycho-social response had been initiated - including ways of talking about Covid-19 with children who are distressed or worried.

Dr Bloomfield confirmed that the Ministry of Health will have a third of its staff working from home for the next week on rotation to increase its resilience.

He said the Ministry was not looking at a lockdown at the moment. He said it was doing everything it can to avoid having community transmission but was prepared to act early as necessary.

Dr Bloomfield said some elective surgery was already being postponed to allow staff training.

As Covid-19 spreads around the world, it can be daunting keeping up with the information. For RNZ, our responsibility is to give you verified, up to the minute, trustworthy information to help you make decisions about your lives and your health. We'll also be asking questions of officials and decision makers about how they're responding to the virus. Our aim is to keep you informed.

Dr Bloomfield told Morning Report today the Health Ministry was setting up a centre to focus on tracing the close contacts of those who had been infected.

He said he had no doubt New Zealand would see more cases arriving from overseas, and hundreds of contacts were being sought.