Routine testing for Covid-19 across the country will be rolled out to provide more clues about whether there is community transmission, Health Minister David Clark said.
It will become part of the normal routine for testing for the common flu, and comes amid uncertainty about whether Covid-19 is being transmitted in the community.
The Government has defended the number of tests conducted so far, saying the capacity is there and it is up to the clinical experts to decide who to test, taking into account symptoms, travel history and close contact with people suspected of having Covid-19.
But only about 500 tests had been done until this week - though another 500 tests were done yesterday.
The number of cases would expect to rise exponentially if there was community transmission, but with only 12 confirmed cases, there is no evidence of such transmission.
That didn't mean community transmission wasn't happening, public health expert Professor Michael Baker said.
"The big concern at the moment is we haven't done enough testing in New Zealand to know whether we've got transmission in the community," Baker told RNZ this morning.
"I think we'll breathe a huge sigh of relief once we've done 20,000 tests or so around the country of people with symptoms, and then we can be much more certain about whether we have community transmission happening."
Baker said it was a good sign that hospital ICUs were not being overrun by sick people who might have Covid-19.
"But unfortunately you have to do a lot of testing to say that something isn't there."
Clark said testing for Covid-19 would become part of common flu-testing, which routinely happens across the country.
"They will also be testing for Covid-19 in a routine fashion. That's across the country. That will give us any indications of community spread."
He didn't know when it would start, but added: "I understand it's to be rolled out imminently."
The Ministry of Health has been asked when it will begin.
Clark said with 500 tests done yesterday, it wouldn't take long to get to 20,000 tests.
Easing the requirements before a test would also help increase the number of tests, he said.
Clinicians had needed sign-off from a Medical Officer of Health before ordering a test, but the Ministry of Health dropped that prerequisite at the weekend.
Clark said he didn't want that step to keep doctors from testing patients who should be tested.
"I don't think it was an impediment in the early stages. We don't want it to become an impediment, having to wait for some kind of permission. So that's why that step was taken early to remove the need for that permission."
Until more testing could be done, Baker said it was appropriate to have social distancing - even closing schools, a step the Government has not taken so far.
Baker said if containment was successful, the ban on social gatherings of more than 500 people and the advice to stay at home could be eased.
If not, he said once "sustained transmission" is reached, it takes about four months to peak and then another four months to drop - "if you do nothing".