"[They] will be spoken to by health officials and given information about how they should self-isolate."
Ashley says health officials will not be be actively monitoring the New Zealanders who have isolated themselves.
He says passengers are being carefully screened before they get onto flights to come to New Zealand.
"The most important part of this border measure is actually the pre-screening that happens at the China end.
"Immigration officials and Customs officials are looking at the pre-screening and at the passenger manifest at the other end to ensure that people who aren't travelling on a New Zealand passport don't actually get on the flight."
Ashley went over recent days there had been a significant increase in the number of people sickened by and killed by coronavirus; and the number of countries with confirmed cases of the disease.
And a new study in the medical journal Lancet describes a person in Germany who was not displaying any symptoms of coronavirus passing the illness onto others.
He says on the basis of the increasing cases and the Lancet study, health officials advice to government is to impose the stricter border measures.
However, China has called the decision "disappointing". China's consul general in Auckland, Ruan Ping, says the sudden decision could hurt the superpower's economy - and that would also be bad for New Zealand.
While the World Health Organisation has declared the outbreak a public health emergency of international concern, it says global trade and travel restrictions are not needed.
New Zealand Customs has announced that e-gates are closed to all incoming international travellers, with people now to be manually processed through Customs.
Terry Brown from Customs says this would cause significant delays for incoming travellers.
He says staff would wear protective gear and stand a metre away travellers in a bid to stay staff.
Wuhan evacuation of NZers
St John is sending a doctor and two paramedics on a government-chartered flight to Wuhan to evacuate New Zealanders at the epicentre of the coronavirus outbreak.
It says the team - which departed Auckland on Monday - would provide infection screening, clinical advice and treat any returning passengers and crew.
The Air New Zealand plane has reached Hong Kong but no further details about the flight are available yet, including the number of people who will board the plane.
Air New Zealand will also have a doctor on the flight.
Ashley says the Ministry of Foreign Affairs and Trade is still firming up how many people will be on the evacuation flight.
He says people will be given masks and instructed on how to move around the plane to avoid spreading any illness.
Any people displaying symptoms of coronavirus won't be allowed on the plane, he says.
Australians, Tongans and Samoans will also be allowed on the plane.
The New Zealand and Pacific Island evacuees will spend 14 days in isolation at a military facility in Whangaparaoa in north Auckland.