New Zealand's total number of coronavirus cases has jumped to 368, says Director-General of Health Dr Ashley Bloomfield.

Health officials identified 85 new cases of Covid-19, including 76 new confirmed cases and nine probable cases.

There are currently eight people in hospital across the country, including the first patient with Covid-19 in intensive care in Nelson hospital.

Three people are in Wellington regional hospital, two in Nelson hospital and one in Waikato, Auckland and Whangarei hospitals.

Six of the patients were in a stable condition and two were in "a less stable condition".

The person in ICU had been ventilated because they had a "significant" underlying health condition, Bloomfield said.

The other person who was not in a stable condition was in Wellington.

Most of the cases are still related to overseas travel. There were no new clusters being investigated other than those from Thursday.

There were 37 individuals who had now recovered, he said.

The definition of "recovered" was getting over your symptoms and staying symptom-free for a 14-day period, Bloomfield said.

Laboratories were working at pace to process and report test results as quickly as possible, he said.

In the past seven days, an average of 1479 had been processed each day.

Discussing Personal Protective Equipment, Bloomfield said there had been a lot of calls from doctors and nurses and other healthcare professionals saying there was not enough PPE to go around.

He was assured there was plenty but it wasn't always in the right place.

"We have PPE available right throughout our system," Bloomfield said.

There are more than 18 million masks across the country and another five million spread around DHBs.

In addition, the Ministry of Health's national reserve currently held 1.9m aprons and gowns, 2.7m pairs of gloves and 60,000 sets of eye protection.

"The ministry is currently exploring existing and a range of new avenues to ensure we maintain our stock."

This included having productive conversations with senior private sector people who had good international networks.

"All stones are being turned over to make sure we keep our stocks at the levels that will be needed to protect our healthcare workforce and essential workers," he said.

The ministry would be sending out updated guidance to health professionals on when to use PPE, he said.

Similar advice would also be provided for essential workers. This would include information about the use of masks and hand hygiene measures.

Bloomfield repeated his call for retired medical staff and others not currently in work to call in and help if possible.

Going into the weekend Kiwis should do their best to take care of their families by staying active (within their bubble) but otherwise staying home, he said.

It comes as the country begins a four-week lockdown to break transmission of the virus.

Bloomfield was joined by Civil Defence Emergency Management director Sarah Stuart-Black thanked most Kiwis for obeying the new rules.

"We have a critical window to save lives and secure New Zealand's future," she said.

"We understand this places strain on you and your families. The sacrifices you make will save lives."

Health officials say it is hard to predict how many Covid-19 cases there would be in New Zealand but it may get into the thousands.

People without somewhere to stay should contact Work and Income to look into temporary accommodation, she said.

People could also call or text 1737 to discuss any mental health issues.

Bloomfield has previously said it could take ten days of strict lockdown to see a decline in the climbing coronavirus numbers.

"These are unprecedented times for this country, and indeed people around the globe ... We would expect the number of Covid-19 cases to increase in the coming days," he said on Thursday.

Triggers that could enable a move down alert levels - "to alert level 3 and potentially 2" - were being watched for carefully.

Even if we do drop back to a lower alert level, it was possible New Zealand might have to re-enter a lockdown state in the future, Bloomfield said.

"That's why we are looking to see what we might need to do to come out of the current arrangements, and then also we're also looking to countries like China to see, as they come out of what appears to be a successful lockdown arrangement what things they put in place to prevent getting a further increase again."

It was hard to predict how many Covid-19 cases there would be in New Zealand but it may get into the thousands, he said.

New research suggests up to 80,000 Kiwis could die from coronavirus without strict measures such as the country-wide lockdown.

It also shows that the lockdown may have to last far longer than a month to keep the strain on the healthcare system manageable.

But one of the paper's authors said New Zealand's speed at adopting a lockdown could mean we "stamp out" the disease much faster.