Disturbing theory about Sydney outbreak
An asymptomatic vaccinated hotel quarantine or medical worker could be the missing link in the NSW mystery COVID-19 outbreak, say experts - but we might never know.
NSW authorities are scrambling to work out how a man in his fifties contracted coronavirus that genomic sequencing has traced back to a returned traveller who tested positive in hotel quarantine.
NSW health authorities have given themselves 72 hours to find the missing link between the man from Sydney's eastern suburbs and a passenger who returned from the US before harsh restrictions are relaxed.
The man tested positive on Wednesday, and his wife on Thursday.
Quarantine hotel workers and medical staff that are vaccinated against COVID-19 can potentially be asymptomatic and inadvertently spread the virus, says Professor Peter Collignon, from the Australian National University Medical School.
Being asymptomatic would reduce the chances a person would see the need to get tested, as they'd have no indication they were sick.
Dr Collignon said it was possible to contract the virus off a vaccinated person, but it would likely be a less harmful strain of the disease.
"In some ways, it's more likely (to be a worker associated with hotel quarantine), because the majority of people associated with quarantine and with the transport of returned travellers are vaccinated," Professor Collignon told NCA NewsWire.
"Unless this ends up being from an overseas aircrew or something.
"The more we have quarantine workers vaccinated, the more of a chance one of these episodes will be related to someone that is vaccinated.
"By the same token, if we had 10 episodes due to quarantine workers before, once they're vaccinated, instead of 10, we may have two or three and (those infected) have a less severe infection and a shorter time of spreading the virus."
NSW chief health officer Kerry Chant said has conceded so far they "can't find any direct link between our (cases)".
"So what we're concerned about is that there is another person that is yet to be identified that infected our case," she said.
In late March, a vaccinated Brisbane nurse, who was part of a cluster that forced the city into lockdown, had tested positive while showing no symptoms.
"She does work on the ward and she was tested as part of the asymptomatic screening testing process for that ward and was found to be positive," Queensland's chief health officer Dr Jeanette Young said in March.
"She has since developed some symptoms, but she was part of that testing."
Australian Medical Association vice-president Dr Chris Moy said he could not rule out an asymptomatic quarantine worker being the source of the spread.
He said stifling the outbreak of coronavirus was all about reducing probabilities and that's why it was vital for people to get vaccinated against the disease.
He said the vaccine may create asymptomatic spreaders, although their strain of the virus would be significantly less potent than in someone who had not been vaccinated.
"Everything has to be on the table and they have to consider it, but I suspect it may be something they haven't discovered.
"It's a probability game and the probability to transfer the infection if you are vaccinated is much lower."
Both Dr Moy and Professor Collignon said it was imperative that anyone who had been vaccinated still get tested regardless of how mild the symptoms were.
Originally published as Disturbing theory about Sydney outbreak