There have been 58 new confirmed and probable cases of Covid-19 in New Zealand in the past 24 hours, with 74 people now recovered.

Director-General of Health Dr Ashley Bloomfield said that with the 58 new cases, there have now been a total of 647 cases in New Zealand.

"Whilst this is a drop in the [daily increase] number over the last day or two, I have no sense that this is a drop overall and our expectation is that the number of cases will continue to increase."

He said the lower number could be partly attributed to fewer couriers working on Sunday, which could have held up test results.

He said 14 people were in the hospital with Covid-19 - two of them in intensive care in a stable condition.

"We have more testing capacity coming on board later this week, with additional labs taking up testing as well."

He said health authorities were still "seeing that strong link in positive cases to overseas travel".

About 1 to 2 per cent of cases were community transmission, Dr Bloomfield said.

He said authorities had some idea of where the community spread was, but they were working to build a picture.

He said he could not be certain Covid-19 was not already transmitting through hospitals - but the first death of a person in New Zealand with the virus yesterday had triggered changes in the way respiratory illnesses are treated.

The person who died was a woman in her 70s who had other underlying illness and was being treated for influenza before she was tested for Covid-19.

Dr Bloomfield said the modelling reports painted a sobering picture of what the impact of Covid-19 in Aotearoa would be if a strict approach was not taken.

"Without the actions currently being taken, the uncontrolled spread of Covid-19 would exact a high price on New Zealand in terms of its impact on our healthcare system, on our healthcare workers, and of course, in a large number of deaths."

New Zealand needed to take this virus seriously, he said, and part of taking it seriously was getting the best possible outcome from the level four measures put in place.

He also noted that there had been a lot of ongoing interest in personal protective equipment.

"It's very important that we keep our frontline health workers safe and there has been very clear advice about where healthcare workers need to wear PPE in different contexts. However, I'm also conscious that our frontline health workers not only need to be safe, they need to feel safe.

"I know that many of our frontline healthcare workers are concerned about not having access to masks when they feel they need them to feel safe."

Director of Civil Defence Emergency Management Sarah Stuart-Black has also spoken after the State of National Emergency, giving extra powers to the state, was extended this afternoon for another seven days.

She said a Covid-19 Local Government Response Unit had been formed, and regional Civil Defence groups would be operating local hotlines around the country.

"I'd like to thank everyone for all you're doing to help stop the spread of Covid-19. The small things we do as individuals make a real difference.

"Please keep being kind, we're all in this together. People who have or suspect they have Covid-19 need to be treated with compassion and support. No one catches this virus on purpose."

She also pointed out that wet wipes were a major problem for councils' sewers and wastewater treatment plants.

"As people, rightly, become more vigilant about hygiene, the use of wet wipes has increased markedly. Unfortunately, disposing of wet wipes down the toilet leads to extra blockages in the sewer network - and this includes flushable wet wipes.

"The bottom line is, if you'll beg my forgiveness, please always put wet wipes in the rubbish and not in the toilet."