The Sofrana Surville, a ship bound for Brisbane from Auckland and Noumea, is the most likely source of infection for a port worker who tested positive for Covid-19 last week.
The Ken Rei, a ship off the coast of Napier with 21 crew on board, was also being looked at, director general of health Ashley Bloomfield said today.
The marine electronics engineer had worked on both ships - but at this stage Bloomfield said there was no sign of any further infections, and thus no need to change alert levels.
It was revealed yesterday the engineer had tested positive for the disease. It was the first community case in New Zealand since September 24.
There are no new cases of Covid-19 in New Zealand today, Bloomfield said in a press conference today.
Genomic sequencing showed the strain of Covid-19 had not been previously seen in New Zealand and was not linked to the recent August outbreak or any other New Zealand cases, he said.
Bloomfield said there were 29 close contacts of the man, including 21 on the ship off Napier, four household contacts, three port workers in Taranaki, and one workplace worker.
They will all be in isolation for 14 days, regardless of a negative test.
Test results of one workplace contact and two of four household contacts had tested negative, Bloomfield said.
Two other household contacts were awaiting test results.
Ship bound for Brisbane
Bloomfield said the most likely source of infection was a ship the man worked on in Auckland on October 12 and 13.
The Sofrana travelled from Brisbane to Tauranga and then to Auckland, where eight crew joined it from the Philippines. They had flown into New Zealand and were released from managed isolation on October 13.
The man was wearing PPE while working on board on October 13.
The Sofrana then went to Noumea and is on its way to Brisbane.
There are 19 workers on board and they might be tested when they arrive in Brisbane, though Bloomfield said that would be up to Brisbane authorities.
Bloomfield said he was interested to see if any workers on board would test positive.
He said the ship normally travelled all around the Pacific, so crew could have been infected while travelling. They could also have been infected by the new crew from the Philippines who joined the ship in Auckland.
Ship off Napier
The Ken Rei, which only operated in NZ waters and with only a NZ-based crew, was also a possible source of infection - though less likely.
That ship is currently anchored off Napier and all 21 workers on board are being treated as close contacts. The man had been working on equipment on the ship on October 14.
Crew members were receiving daily health checks, Bloomfield said. None had any symptoms so far.
The port in Napier did not want the ship to berth, but Bloomfield said that wasn't a source of frustration and he was happy for it to be anchored off the coast while the next move was being resolved.
He did say, however, that it was risk to have them all on the ship in close quarters for an extended period of time because of the risk that all of them could easily become infected if one of them had Covid-19.
What to do if any of the crew tested positive was still being worked through, he said.
"There is urgency," he said, adding that options were being considered for testing the 21 people on board.
A helicopter could pick them up or the ship could be sent to Auckland, he added.
Pop-up centres were being set up in Auckland and in Taranaki for people to be tested if they wanted. Staff in hotels where the man stayed in New Plymouth were also being tested.
Bloomfield said the current port safety measures were "very good" and included regular testing, including those who accessed ships.
But the entire process would be looked at to see if anything needed to be improved.
Bloomfield said the infected worker was being tested fortnightly, and one thing to look at was whether such workers should be tested two to three days after finishing a long shift working on a ship.
Another was whether workers should have shorter shifts. The worker had been on the ship for six-hour shifts.
Overall there have been 1530 confirmed cases in New Zealand. There are 37 currently active cases.
Yesterday, 1373 tests were conducted.
No need to change alert levels
Prime Minister Jacinda Ardern said yesterday there was no need at this point to change alert levels, and that border controls were working as they should because the port worker was being regularly tested.
Those tests had all come back negative, and he was due for his next test on Friday.
But he had become ill three days ago, on Friday, called Healthline, and was tested later the same day.
A positive result was returned on Saturday. Bloomfield informed Health Minister Chris Hipkins just after 6pm, less than an hour before voting stopped.
Bloomfield said yesterday the man was potentially infectious on Wednesday and Thursday, when he was working in New Plymouth on the Ken Rei.
He had driven by himself from Auckland to New Plymouth on Tuesday, stayed in two rooms while there, which had since been deep-cleaned, and then driven back to Auckland on Wednesday evening.
"So far there is no evidence of any onward community transmission," Bloomfield said yesterday.