Health Minister Chris Hipkins says it is reasonable for testing advice to change as more information comes to light in the face of the latest Covid-19 cases.
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Two crew of the Sofrana Surville cargo ship anchored off the Sunshine Coast have tested positive for Covid-19.
The Ministry of Health says the ship is the most likely source of infection of two New Zealand port workers who were aboard it when it was in New Zealand about 10 days ago.
It has not yet been confirmed whether the ship's cases are genomically linked to the New Zealand port workers.
Health Minister Chris Hipkins told Checkpoint it appeared the cases on the cargo ship were at different stages of infection.
"One of them was a negative PCR test but a positive serology test, and other one was a weak positive PCR test and then a positive serology test.
"They're all at different points in the infection cycle, which would lend itself to the idea that the virus has been circulating around that ship and that would suggest that is the most likely source of infection for the workers who've worked on it."
Covid-19 testers in Auckland have been run off their feet on the North Shore after news that person unknowingly had the virus when they went to the Malt bar in Greenhithe on Friday.
The Ministry of Health has stepped up its advice on who should get tested. Initially it said anyone at the pub should get a test. Now it says the contacts of all those pub-goers should too.
Hipkins this morning said that person had been exposed to the virus earlier that same day, so the risk to the public was low, but clarified it was possible they had become infected earlier than that.
"At this point we can't discount the possibility, given that it's a work colleague, or someone who's worked in the same building as the two people as cases A and B, you can't discount the possibility that it could have been slightly earlier than that. So we just want to make sure that we're not leaving anything to chance at this point."
The ministry had previously said the port worker had a very short exposure to the person who went to the pub a - about three minutes in the same room as them, but experts have been challenging that.
Microbiologist Dr Siouxsie Wiles said on Twitter: "If someone in NZ really did get infected after just 3 mins contact then looks like we’re going to need to be isolating all casual contacts as well as close, or redefining what we mean by close."
"New information comes through all of the time," Hipkins said in response.
He said however that the person had met with another case who was a colleague of the port worker, and this could be another possible source of infection.
"That [three minutes] was certainly one of the possibilities was when we were dealing with case A only, and case C is one of the people who works in the building. They'd only come into contact for about two minutes on the Friday.
"On the other hand case B, which initially was not known about - this was someone who tested positive a bit later in the process - they did have a longer period of contact with that person (case B) on the Friday.
"They were in a meeting together. So, it's possible that could have been a chain of infection there, rather than the two-minute fleeting contact," Hipkins said.
"We're testing absolutely everybody all of these people have come into contact with."
The Health Minister said the numbers of how many people at the Greenhithe pub have been tested will be available soon.
He said he was not disappointed at the official messaging on testing.
"I think it's really important to note that you get new information all the time, so when the first random information was released publicly we weren't aware of case B.
"Case B tested positive relatively late in the initial investigation process. So at this point that could well be the link between cases A, B and case C.
Despite the outbreak, Hipkins said mandatory masks on public transport was not being considered, but if the outbreak appeared to broaden further, then it would be looked at.
Regarding another 18 Covid-19 cases among the Russian fishers at the Sudima Hotel isolation facility, Hipkins said he had not seen the photos of the crew-members on balconies close together, smoking and leaning over the railing.
"We're looking very closely at those arrangements to make sure they're as robust as possible," he said.
"My understanding is that the next charter flight [from Russia] will not depart, it will not come to New Zealand, until we have space to be able to accommodate those people, which obviously is difficult when some of those people who are currently occupying those beds are likely to be staying there for longer.
"We're not in the position to receive them at the moment."