He's quick to reassure people the cases were all linked to other countries, meaning no community transmission has yet been detected.
"All these cases, as we said yesterday, are associated with overseas travel and of course over the last week or two we have seen people coming back from areas that have got outbreaks."
He told RNZ's Morning Report more cases like that were expected.
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He says there are now hundreds of close contacts being sought, and the Ministry of Health is setting up a centre to handle that work.
"I have no doubt there will be more cases and that's what we would expect at this time and that's why we saw the big increase in cases yesterday, all associated with people coming back from overseas.
"We're now establishing a national approach to close-contact tracing to support the public health units and we'll be setting up that process here in the Ministry of Health so that the public health units find the cases and then get the right information and then we do all the close contact tracing from the centre."
"It's really pretty tight on the border and the number of arrivals has gone down considerably."
He says all the measures being considered are being worked through by officials and politicians.
"Everything's on the table ... the challenge here is to think what you might need to do in two weeks then bring it forward and do it today.
"We've already had that cap put on gatherings of 500 and the Prime Minister's been clear that she's going to make further announcements about this, probably today.
"I think the key thing here is the gatherings is part of a suite of things that all New Zealanders really need to contribute to, which is that physical distancing - and that's going to be really important."