Labour MP and Minister Nanaia Mahuta is the latest MP to be in self-isolation - though none of the four MPs are showing any symptoms of Covid-19.
Mahuta was in Canberra at the weekend to attend a kapahaka performance at a public event, and returned to New Zealand before the new travel restrictions kicked in at 1am this morning.
But she decided to take a precautionary approach and self-isolate, even though she has no symptoms.
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That is also the approach taken by National MP Chris Bishop, who has self-isolated after coming back from Australia on Saturday night.
Mahuta, Bishop, Green MP Chloe Swarbrick, who was also in Australia at the weekend, and NZ First MP and Minister Tracey Martin, who was with coronavirus-infected Australian Minister Peter Dutton last week, are all in self-isolation. None of them have any symptoms.
National MP Kanwal Bakshi is in India and will have to self-isolate when he returns to New Zealand.
Bishop flew to Australia on Friday morning to watch the one-day cricket international between Australia and New Zealand, landing there just after the game was announced as being spectator-free.
He returned from Australia well before the 1am deadline when the new travel restrictions began, and went into self-isolation on the advice of Healthline.
"They said, 'There's no legal obligation but we would prefer that you did,' so I am doing that for the next 14 days," Bishop said in a video post he put on his Facebook page.
"I'm fine, I have no symptoms of coronavirus at all, but I'm following the advice of the authorities."
Bishop, who is the Hutt South MP, said he was sad to miss a number of community and public events - such as fun runs, a club cricket game and a school gala - and he would be absent from Parliament for two weeks.
"Sorry in advance to people who were expecting to see me at events. I will be contacting event organisers personally to pass on my apologies.
"If you live in Petone, you might see me walking the dog along the foreshore or maybe going for the occasional run. The advice is that's okay, but for the most part I'll be working from home."
Yesterday Swarbrick said she will self-isolate for 14 days, having been in Australia at the weekend.
"I have been overseas and as such will be following the protocols outlined by the Prime Minister," Swarbrick said today.
"These protocols were designed to keep everyone healthy. I do not have any symptoms, but I am registering my whereabouts with the Ministry of Health and will be following advice."
Martin is also in self-isolation, after meeting with Australia's Minister for Home Affairs Peter Dutton during a Five-Eyes partners meeting in Washington DC.
Dutton had no symptoms of Covid-19 at the time, but woke up with a temperate and a sore throat on Friday. He has since tested positive for the respiratory virus and is now in hospital.
A spokesperson for Martin said she had shown no symptoms, but was self-isolating as a precaution.