Director general of health Dr Ashley Bloomfield told Newstalk ZB's Mike Hosking the Ministry is "assuming they were infectious in Wellington". Video / Newstalk ZB
After recording 10 new coronavirus infections on Tuesday it's the question on every NSW resident's mind: Is Sydney heading for lockdown?
Last month Melbourne shut down after its outbreak hit 26 cases, with the state recording 12 new infections on the day restrictions were announced.
As of Tuesday NSW has21 cases now linked to the Bondi cluster, which can be traced to a limousine driver responsible for ferrying overseas flight staff.
The only mystery case is a child who attends St Charles Catholic Primary School at Waverley, with investigations under way into how the student acquired the highly infectious Delta strain.
One coronavirus expert has warned that failing to implement a lockdown quickly could prove to be a big mistake for NSW as the current mask measures only had a 50 per cent chance of success.
NSW Premier Gladys Berejiklian announced a week-long extension of mask restrictions to all of Greater Sydney after the worrying rise in Covid-19 cases on Monday.
But ABC reporter and medical expert Dr Norman Swan said the reason Sydney wasn't in lockdown was because there hadn't been "too many surprises" in the outbreak so far.
Dr Norman Swan appeared on The Project. Photo / Channel 10
"Significant numbers are occurring while people are already in isolation, and you also know the chain of transmission … [there's] only one mystery case," Swan said on Tuesday night's episode of The Project.
"People are going to say, 'Oh, why is Sydney not locking down when Victoria did?'
"It is very different circumstances, because in Victoria you have the Wollert man and you had a broken chain of transmission … whereas here there's an unbroken chain of transmission, we know where it came from and that is luck actually – unlucky in Victoria."
But Swan stressed that future lockdowns in NSW and other states were still a "significant possibility" until mass vaccinations occurred.
"This one, [NSW] are lucky, they know the chain of transmission and they can control it. Next time, maybe not," he said.
"It is not about numbers, it is about where people have caught it and where they've passed it to."
Swan's comments echo those made by Berejiklian, who confirmed the number of unlinked cases would determine if a lockdown was needed.
NSW Premier Gladys Berejiklian said a sharp increase in unlinked cases would be cause for concern. Photo / News Corp Australia
"All but one case is linked to an existing case and that case was only discovered a few hours ago … that gives us a degree of confidence that what we have asked people to do matches the risk that is there at the moment," she said.
"If that changes, if we suddenly have a number of unlinked cases and if we suddenly have them outside the geographic region they are concentrated in that we will obviously adjust the health advice and we will respond to that [idea of a lockdown]."
Berejiklian has announced a week-long extension of mask restrictions to all of greater Sydney, with masks compulsory on public transport and indoor venues until midnight on Wednesday, June 30.
The mandate has also been extended to greater Sydney as well as the Blue Mountains and Illawarra regions.
