Microbiologist Siouxsie Wiles is urging New Zealanders to get the message not to visit friends or family - or they will risk extending the lockdown.
Speaking to RNZ's Morning Report today, Dr Wiles said it was essential that people understand the need to avoid contact with anyone outside their own household.
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"People are not understanding - there are no dinner parties, there's no popping over to someone's house for coffee.
"People are the weak points. I'm hearing people say 'oh I'm just gonna go and visit my friend' or 'I'm just gonna go and visit my family'.
"You are in a bubble... our own household is our bubble and you need to stay in your bubble and if you go out of your bubble you're going to pop that bubble and that's going to put us all at risk."
She said the important thing now was for everybody to get the message about how important the lockdown was.
"If they don't get that message our lockdown is gonna be longer than four weeks, because every person that breaks a bubble means that we're gonna need to do this for longer.
"What you mustn't do is assume that we can go with a friend and have dinner or go and pop round to our family's house. That is not allowed."
How to practice safe hygiene when going to the supermarket
Dr Wiles said it was understood that people needed to be able to get supplies.
"We can go outside and we can do these things as long as we keep it to essential trips, stay two metres away from people; we can pick up our groceries and things."
Even when picking up goods at the supermarket, there were things people could do to protect themselves and others.
"We want to minimise our time outside the house ... doing a bigger shop - if you can do a bigger shop that would be better, that would allow you leave time for your groceries to sit for a few days.
"We know that the virus can survive on surfaces for up to three days ... on cardboard it's about 24 hours.
"If you're bringing your shopping in you could just leave your non-perishables for a few days before you use them, or you can wipe them down even with just a soapy cloth or something.
"Your fresh things you can, if you're worried about them, just give them ... a little bit of a soapy wash and rinse them off."
"We need to wash our hands as soon as we get back in the house."
Outdoor activities without breaking the bubble
She said people could undertake outdoor activities with those in their household, as long as they avoided anyone who was not in their household.
"You can go for a jog with ... your bubble family. You can go for a drive to the beach with your bubble family. But you must not enter anybody else's bubble."
She said some more dangerous activities should be avoided, however.
"The coastguard are also in bubbles so ... please if you have a boat or you're gonna go surfing don't do those things.
"We don't want you to do anything that's gonna endanger you when we don't have the services there to look after you. Don't make their job - the coastguards' job - more difficult."
She was hopeful the virus in New Zealand would peak soon so the country could return to business as usual, hopefully in the next two to three weeks, possibly four.
"We know that we're running on this sort of two-week timeline where what we're seeing now is what happened two weeks ago, and because there's more Kiwis coming in from overseas the numbers of cases associated with travel will continue to rise.
"We'll also presumably see a number of increases in terms of community transmission but what we're doing now is putting the brakes on and so we should see the benefits of this in hopefully two to three weeks, maybe four weeks."
The other thing that was important was contact tracing for all new cases. Dr Wiles said she was confident New Zealand had the capacity to get it right.
"It's just a case of ramping up but also training the people to do it, so I've every confidence that once all the right people are in place that this is something that we can do."