The risk of a major Delta outbreak from the infected crew of a ship moored off Tauranga is described as low, but many elements remain unclear.

The best-case scenario, according to Professor Michael Baker, is that few or none of the 11 crew members who tested positive are contagious, and the 92 port workers who have been in contact with the ship – the Rio de la Plata – do not. have not done. catch the virus.

In the worst-case scenario, workers caught the Delta variant from the crew members Wednesday night, when the ship docked, and spent just over four days circulating the virus in their respective communities.

But the odds of that appearing “relatively low,” Baker said, given that crew members are not symptomatic – and therefore may not be infectious – and port workers appeared to have followed the proper protocols, including wearing PPE.

The 21 crew members were all tested before they could make it to Napier port, and 11 positive results were returned yesterday morning. They all remain on board off Tauranga.

Prime Minister Jacinda Ardern did not give an assessment of the level of risk yesterday because there were still many unknowns.

Among them was the sequence of events – including whether the crew had been tested before arriving in Tauranga – and whether workers should have been told to return to work on Thursday after being ordered to self-isolate on Wednesday evening.

Yesterday, Ardern said she had yet to receive an answer as to why they had returned to work despite a known link to a Delta case; a ship pilot boarded the Rio de la Plata in Queensland in July and tested positive nine days later.

Wednesday night’s isolation order was based on “great caution,” the Department of Health said, after being briefed on the ship’s pilot in Queensland.

But on Thursday, workers returned to work following health advice that it was “extremely unlikely” the pilot had infected the ship’s crew as he was not contagious while on board.

Baker said it was possible the ship’s crew had circulated the virus between them for weeks, infected the pilot in Queensland and were no longer contagious by the time they reached Tauranga.

“The ship could have suffered chains of transmission, potentially for several weeks, but they could have largely burned. There could be very few, if any, infectious people on board,” he said.

“The fact that there are no symptoms is positive. People may have ruled out the infection and still test positive for several weeks or even months.

“There are quite a few things on our side so that this does not turn into a major epidemic. “

He said there was no need for port worker households to self-isolate unless there is evidence of transmission, although this could be done as a precaution as the threat of an epidemic of Delta is so dangerous.

“With Delta, by the time you have proof of transmission, it may be too late.”

The Health Ministry initially said 94 port workers had been in contact with the ship, but later said there were 92 as it was discovered that two customs workers were not at hand. edge.

Six additional port workers were identified as potentially at risk and were also tested. As of yesterday afternoon, 23 of the 98 had tested negative.

The case highlighted the low vaccination rates of frontier workers, including at ports. Only nine of the 98 workers are fully vaccinated, two have received a dose of vaccine and the vaccination status of four workers is still being verified.

“These numbers are too low,” said Covid-19 Response Minister Chris Hipkins, who has expressed concern about port workers in particular for more than two months.

Frontier workers employed in a private capacity must all be vaccinated before September 30 or they will not be legally allowed to work at the border, but certain exemptions may be granted.

Port officials suggested exempting ship pilots, who are not so easily replaced if they are not vaccinated and cannot work as pilots.

Hipkins said no exemptions had been granted at this point and the threshold was “very high”.

The September 30 deadline has been questioned as being too lenient, and while Hipkins said she was constantly watched, the timeout helped to combat misinformation and hesitation about vaccines.