Ruby Princess passenger may have acquired virus in Qld, not on the cruise ship: virologist

A leading virologist has raised new concerns about the extent of coronavirus community transmission in Queensland, after casting doubt on a case where a passenger from the Ruby Princess cruise ship tested positive - two months after she disembarked.

A Cairns Ruby Princess passenger, who tested positive to pandemic coronavirus more than two months after her cruise, may have been infected in the community rather than on the ship, a respected Queensland virologist has warned.

Griffith University’s Nigel McMillan said it was unrealistic to believe the virus had been incubating in the woman’s system since March 19, when the Ruby Princess docked in Sydney, and she had only just started to experience symptoms.

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The Ruby Princess cruise ship, docked in Sydney on March 19. Picture: Dean Lewins, AAP.

“I’m not saying it’s impossible, I’m just saying it’s incredibly unlikely,” he said.

Professor McMillan said the longest incubation period for the virus reported out of China was 27 days, with “99 per cent of people” showing symptoms no longer than 14 days after infection.

“From my point of view, this story tells us that we can’t be complacent. Clearly, there may be community transmission that we’re unaware of,” Professor McMillan said.

Three Cairns cases since the start of the pandemic are listed as having been locally acquired with public health officials unable to trace the source of infection.

While not ruling community transmission out in the latest far North Queensland case, Professor McMillan agreed with the state’s Chief Health Officer Jeannette Young that another possibility was the infected woman, in her 60s, had been shedding dead virus particles “for quite some time”, resulting in her positive test this week.

Queensland Deputy Premier Steven Miles with the state’s Chief Health Officer Dr Jeannette Young. Picture: Darren England, AAP.

“I think it’s far more likely given the large number of cases that we have seen on the Ruby Princess that that’s where it was acquired,” Dr Young said yesterday.

Professor McMillan said research out of South Korea had found COVID-19 patients continued to shed dead virus from their lungs while they were recovering.

He said the genetic tests used to detect the novel coronavirus in Queensland were unable to indicate whether the patient was still infectious, lending support to the theory that the woman may have tested positive to dead virus.

The woman is one of more than 600 Ruby Princess passengers who have tested positive to the novel coronavirus, including more than 20 people who have died after leaving the cruise ship.

Three of Queensland’s seven deaths linked to COVID-19 had travelled on the Ruby Princess.

Griffith University virologist, Professor Nigel McMillan. Picture: Jerad Williams.

Professor McMillan warned Queenslanders to expect to keep seeing cases of the virus until an effective vaccine was developed.

“As long as we’ve got a hospital system that can deal with it, this is how we’re going to limp along for the next year or so or until whenever a vaccine comes along,” he said.

“There are cases around and we’ve just got to deal with them as they come up. The main issue is going to be if this starts popping up a lot more, we might go backwards in our controls and you can see the issues around industry kicking up about border controls. From an infectious disease point of view, border controls make complete sense.”

Professor McMillan said he was concerned Queenslanders were becoming complacent about the virus.

“I’m feeling an apathy in the public,” he said.

“We need to make sure that we don’t because these are examples of things that can happen.”

Queensland has recorded 1058 cases of the new virus, with just seven active infections remaining. Four people are being treated in Queensland hospitals with COVID-19, one of them in intensive care.