An infectious disease specialist says more people with coronavirus could already be in the community and might be silently transmitting the disease.
An Auckland woman has Covid-19 but wasn't diagnosed until eight days after she arrived from northern Italy. In that time she took a return flight to Palmerston North.
Work is under way to trace the passengers sitting near her - and anyone else she may have been in close contact with.
She arrived before the requirement for travellers from northern Italy to isolate themselves was in place.
Public health professor Michael Baker told RNZ health correspondent Rowan Quinn similar situations are likely to arise.