Five cases are linked to the Avalon cluster and one to a medical transport worker who most likely caught the virus from one of the COVID-positive returned travellers they were moving.
The tenth case is a man from western Sydney whose source of transmission is under investigation.
On Thursday, Premier Gladys Berejiklian addressed the daily barrage from epidemiologists, commentators and nervous members of the general public to launch a preemptive strike against the risk of a major outbreak by implementing harsher restrictions on Greater Sydney.
Victoria’s decision to reintroduce mandatory masks for public venues from 5pm on Thursday after recording an additional three cases – believed to be linked to Sydney’s outbreaks – had added further pressure
But Ms Berejiklian said NSW was trying to “strike the right balance” and will instead rely on the community to take up the strong recommendation to wear a face mask in all public indoor settings.
The Premier said she would not hesitate to make any necessary changes, including harsher restrictions, “quickly and nimbly and flexibly” if her expert health advice dictated it.
But she had “complete confidence in team NSW and the way we are approaching this”.
“Of course, should there be something that comes along … should we need to adjust our policy settings we will,” Ms Berejiklian said.
NSW Chief Health Officer Dr Kerry Chant said her position on any tightening of restrictions – including a Greater Sydney lockdown – would shift as new data emerged and the risk level changed.
“Until we got the Croydon cluster we were on a more pleasing trajectory … but if we start seeing cases where we don’t know the source of, particularly in the presence of low rates of community testing, that really elevates our risk threshold and it means we will be having to take even more precautionary actions,” Dr Chant said.
Professor Mary-Louise McLaws, epidemiologist and infectious diseases control expert at UNSW, said the reliance on the public’s willingness to wear masks because they were “strongly recommended” was a misstep.
“I don’t believe in bringing the community along softly, softly when it comes to masks. The science is there,” she said.
“We have an active outbreak so people should be wearing them on public transport and any public indoor space immediately,” she said.
Professor McLaws also foreshadowed the long shadow any infections at New Year’s Eve celebrations would cast for weeks to come, with transmissions overnight potentially being at their most infectious on the first day of the Third Test cricket match.
With a crowd of up to 24,000 people at the SCG on January 7, “I just don’t see the rationale in allowing this potential accelerant event to go ahead,” Professor McLaws said.
“Health authorities remind us again and again that you are most at risk from household contacts, which is why they’ve limited gatherings on New Year’s Eve to five guests,” she said.
“But allowing thousands at the cricket, larger crowds in hospitality venues and not mandating masks on public transport “is failing to acknowledge how the infection gets into your home in the first place,” Professor McLaws said.
Ms Berejiklian said she believed NSW’s response was proportionate to the risk.
“Our first and foremost priority is always community safety, but at the same time we also have a keen eye on mental health, on making sure we will preserve as many jobs as possible and livelihoods as possible and that we bring the community with us,” she said.
“Every decision we take we think about the consequences on our citizens and what it means for them,” she said.
Seven days out from the first day of the Third Test at the SCG, Mr Berejiklian said “we stand by our decision to make sure we can have COVID-safe events … if we need to reevaluate some of the health settings we won’t hesitate to do that.
Emergency Response Expert and Emergency Physician Dr Ian Norton supported the state government’s resistance to a preemptive lockdown in response to it’s “fairly modest cluster”, but the decision to allow crowds at the SCG could be “a superspreader event”.
“We have to see a revision of that decision,” Dr Norton said. “We don’t need to prove we can hold a COVID-safe event. While we still have unrecognised chains of transmission the risk is too great,” he said.
The new detections triggered a suite of new venue alerts throughout Thursday. NSW Chief Health Officer Dr Kerry Chant urged the public to regularly check NSW Health’s website for the updated venue list and immediately get tests and self-isolate if any applied to them.
The Northern Territory reintroduced a mandatory quarantine for Sydney travellers from midnight Thursday, while Victoria will close its borders to New South Wales from 11.59pm Friday.
South Australia will reinstate its hard border with NSW, but Premier Steven Marshall said Victorians would still be able to come and go from the state unfettered – for now.
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Kate Aubusson is Health Editor of The Sydney Morning Herald.