A new gap in Covid-19 border testing has emerged - with foreign workers transitting through New Zealand not being tested for the virus despite spending shorter stays in managed isolation.
It comes after a contractor who was working on a ship in the Ports of Auckland on Monday and Tuesday last week tested positive for the virus four days later.
Eight crew members from the Philippines boarded the same vessel, the Sofrana Surville, on 13 October. They had flown into the country a few days prior, and had spent a brief time in isolation at a Novotel hotel in Auckland.
The Ministry of Health said it is reviewing current measures in place at ports and for ship workers.
However, Director-General of Health Ashley Bloomfield said none of the eight crew members had been tested since their arrival in New Zealand.
"With these crew in transit, we don't routinely test them and that's something we are looking at immediately today with Maritime NZ and transport colleagues over the next few days."
Auckland University associate professor of public health Collin Tukuitonga was surprised by this.
"There's clearly a gap there. Even if you contain these people coming in from overseas, but obviously there's potential interaction with people either on the ship or on the wharf, that's why I would've thought that testing would be mandatory."
Dr Tukuitonga said it showed there were still holes Covid could slip through.
"One would say that that's a failure because even if we had a really tight system, we still can't be 100 percent sure that the risks are not there."
In a statement, the ministry said crew that were flown into New Zealand would be taken straight to the port to join their vessel if it was leaving port that day, after being collected by a vehicle with a driver in PPE gear.
"As they have no interaction with the community they are not required to have a test."
Those that flew in and had a few days before boarding their vessel are taken to managed isolation facilities, the ministry said.
"They isolate at the isolation facility with no interaction with other guests or the community. Once it is time to board the vessel they are driven directly to the port. Testing has not been required as they will complete quarantine at sea."
The Ministry of Health does not yet know how long the infected marine electronics engineer spent aboard the Sofrana Surville, or the extent of the contact he had with crew members.
Before arriving in New Zealand, the ship had stopped off in the Solomon Islands, Papua New Guinea, and Brisbane.
After completing work on the Sofrana Surville on Tuesday, the engineer then headed down to New Plymouth, where he spent six hours of work in the bridge of the logging vessel, the Ken Rei, on Wednesday.
He was being tested fortnightly, but Dr Bloomfield said they were now looking at whether this should be stepped up, particularly for people, like the one in this case, who spend long periods of time working on ships.
"Whilst he's wearing PPE and the crew are wearing PPE, the length of that exposure may mean either more regular testing might be indicated or testing that is associated automatically with a period - maybe two or three days after he has worked on a ship."
The risk to public health is being treated as low.
The man has four household contacts, three close contacts from his stay in a hotel in New Plymouth, and one workplace contact.
All have so far returned negative results, except for two of the household contacts who haven't had their results back yet.
Three Port Taranaki staff members who may have had contact with the engineer have also been tested and are isolating - one has already returned a negative result.
Mayor of New Plymouth Neil Holdom said no-one was taking it lightly.
"The port are taking this very seriously, New Zealand and the health department are taking this really seriously and I think our people are co-operating, because we are proud of what we have achieved as a nation."
Meanwhile, the 21 crew members aboard the Ken Rei are being held up outside of Napier Port.
The Ministry of Health said all were considered to be close contacts, but whether to test them on the ship or to allow them to dock was still being discussed with the port.
Napier Port said its refusal to let the ship dock was in line with border protection measures.
It said it was notified on Sunday morning that the ship had a possible Covid-19 exposure, so it was anchored at sea.
The port said it was on standby to help get public health medical staff get on board, and was working to provide care packages to the crew.
Genome sequencing of the virus type shows it is a new strain not seen before in New Zealand.