New Zealand should shut its borders to everyone except residents to stop the spread of Covid-19, a Kiwi business leader says.

And it's a move the Prime Minister hasn't not ruled out.

Speaking on Friday, Jacinda Ardern said she would not rule in or out further travel restrictions from countries with Covid-19 cases, with decisions expected in the next 48 hours.

But banning flights was not so simple, as medicines were transported into New Zealand on passenger planes, she said. 

The World Health Organisation (WHO) on Thursday declared the Covid-19 outbreak a pandemic, while United States President Donald Trump imposed travel restrictions stopping travel to the US from continental Europe for the next 30 days.

After Trump's announcement, Ardern said New Zealand was reviewing its own travel restrictions every 24 hours and she expected they would get tougher.

Current travel restrictions prevent foreign nationals travelling from, or transiting through, mainland China or Iran from entering the country. On Wednesday, Ardern announced all travellers arriving in New Zealand from Italy must self-isolate for 14 days. Travellers from South Korea must also self-isolate.

But Anna Mowbray, who is chief operations officer for toy company Zuru, said New Zealand's borders should be shut now.

"I don't think New Zealand's doing a lot to slow down the spread of this. I really, truly believe we should be shutting down our borders," Mowbray said.

No-one except residents should be allowed in, she said, and even returning residents - of which she's one - should have a stricter quarantine process.

"I saw what happened in China."

The short-term costs of closing the borders would be outweighed by longer-term benefits, she said.

She's normally based in Hong Kong, where the company is headquartered, but returned to Auckland with her three children about seven weeks ago.

Hong Kong's schools are shut, she said, and home schooling didn't fit well for a working mum trying to run a large company, which she and siblings started in their parents' Cambridge garage and made international.

New Zealand has had five confirmed cases of coronavirus and two probable cases, but no new cases have been reported for six days.

When Mowbray brought her children's nanny over from Hong Kong, she got her to go into isolation - health advice for travellers from Hong Kong is to be aware of symptoms, but that there's no need to self-isolate if well.

And while Mowbray recently went to the US, she said she hasn't been back to Hong Kong since she's been in New Zealand.

Coronavirus has had a huge impact on her company.

Most of the factories Zuru works with are in China and the company had to work hard to get them to reopen fast after shutdowns, Mowbray said.

The first reopened - under strict processes - on February 10, followed by others.

Special measures included workers walking in single file with a 30-second gap between them, dividers between work stations, and metre-and-a-half gaps between people in the break room.

Office-based employees in Hong Kong and China had been working from home until this week, with meetings pushed to virtual platforms.

"We've been very, very cautious about it," Mowbray said.

Moving things around was proving a challenge, as carriers were affected and air shipments were getting congested.

China's government was right to take dramatic steps to control the spread of the virus, and to consider health over GDP, she said.

Mowbray has previously said disruption due to coronavirus had cost Zuru tens of millions.

Other effects include delays in the production of toys the company hopes will be big Christmas sellers, and some new items had been pushed back up to six weeks.

It's now business as usual for Zuru, but they're constantly monitoring for anything which could have an impact on the business.

Mowbray's biggest concern for the moment is figuring out what's going to happen in the United States.

It represents about half of Zuru's sales market and she's conscious that healthcare is not subsidised there, she said.

Mowbray called off Zuru's April toy fairs in Hong Kong and LA about a week ago, in favour of a virtual roadshow.

The company's Italian office is also closed - Italy has the second-highest number of confirmed coronavirus cases in the world and the government has put the country into lockdown.

Zuru is also the sponsor of Balloons over Waikato Nightglow - which will be held at Waikato University on March 20. 

Event organisers said that  they're aware of the evolving situation in regards to the COVID-19 and are continuing to monitor the situation with the Ministry of Health on a daily basis.

"At this stage the Ministry of Health has not imposed any restrictions or does not propose altering arrangements to postpone or cancel any large events or festivals and therefore we will be proceeding with Balloons over Waikato," the event organisers said.