Two of the country's biggest ports are now requiring all international crews to do 14 days in managed isolation - and they want other ports to follow suit.

The ports of Auckland and Tauranga made the move despite Health Minister Chris Hipkins saying today that this would mean a number of ships wouldn't come to New Zealand.

Hipkins told RNZ that every crewmember entering the country could soon be required to be tested for Covid 19 but he's yet to decide whether to put all shipping crews through managed isolation.

The current situation is that crew who are flown into New Zealand are taken straight to the port to join their vessel if it is leaving port that day, after being collected by a vehicle with a driver in PPE gear.

Ports of Auckland's general communications manager Matt Ball said the 14-day managed isolation requirement was introduced last week, after it became clear the likely source of the current port worker cluster was eight Philippine seamen who went through the port untested.

Ball said the port has had a positive response from its shipping companies regarding the requirement.

He said it gave crews and shipping companies reassurance there were no infected people on board.

A Port of Tauranga spokesperson said the company sent an advisory notice to shipping agents last night requiring international crew members joining a vessel in Tauranga to complete 14 days in managed isolation and test negative for Covid-19.

The port understood this created logistical challenges for its shipping line customers, the notice said.

"However, we cannot risk having to close the port due to operational staff being in quarantine."

The Ministry of Health didn't answer specific questions. However, in a statement it said it regularly reviewed the Covid-19 strategy to ensure that it remained fit for purpose for its elimination strategy – this included reviewing what the testing programme for port workers and crew members looked like.

Health officials were working closely with border agencies on how to limit the risk of Covid-19, it said.

Immigration New Zealand said between 10 August and 26 October, 466 individuals were approved a critical purpose visa for the purposes of travelling to New Zealand as 'replacement cargo ship crew'. It said 324 of those individuals have arrived in New Zealand and 142 were yet to arrive.

All international crews arriving in the Port of Tauranga now face a mandatory two-week quarantine. Photo / File

Today marked six straight days of no Covid cases in the community, but health authorities are still questioning how the virus once again slipped through New Zealand's borders.

It's the longest run of no new cases in the community since the marine engineer tested positive for the virus on October 16.

Director general of health Dr Ashley Bloomfield yesterday announced all close and casual contacts of the engineer had tested negative for the virus.

Overall there had been nearly 40,000 tests since the case was announced.

This was despite two of the man's colleagues, who also boarded the foreign vessel the Sofrana Surville, testing positive and visiting a range of Auckland venues including Malt Bar in Greenhithe on the Friday evening, along with a gym, bank and several stores.

While the potential for an outbreak would remain until two full incubation cycles after October 16 - 28 days - so far it appears the city may have dodged a bullet that could have potentially plunged it back into lockdown.

Infectious diseases expert Professor David Murdoch said the main takeaway from the rapid containment of the cluster was that the system is working as intended.

"It has been picked up quickly, we've managed to find the source - unlike the previous outbreak, there's been rigorous contact tracing and genome sequencing."

The fact an infected person had been in a crowded bar on a Friday evening, what could have been a "super spreader" event, and there had so far been no repercussions was not necessarily just luck, Murdoch said.

"Not knowing the exact details, but it appears they'd only been exposed that morning, so that is fairly early on and might be the reason they were not infectious."

Just two new cases of Covid-19 were announced today, both caught at the border.

text by Courtney Winter