NSW Chief Health Officer Dr Kerry Chant said it was critical that anyone who had been to these venues during the exposure period immediately isolated and came forward for testing.
“What we are interested in is that we don’t see further transmission that is not directly linked to the Avalon cluster,” Dr Chant said.
The greatest concern for health authorities would be the emergence of unlinked or mystery cases with no clear connection to the Avalon cluster. Such a case would mean a chain of transmission had been missed and risk undetected spread.
The source of the Avalon cluster is still unknown.
Premier Gladys Berejiklian will make a final decision on Wednesday as to whether restrictions will be tightened over Christmas.
Giving hope is that a record 38,578 people came forward for testing in the latest 24-hour reporting period as testing surged across Sydney and NSW.
The trigger for tougher rules would be evidence that the virus has seeded beyond the northern beaches with increasing numbers of cases detected in other parts of Sydney.
But given the drop in the number of new cases from 30 on Sunday to 15 on Monday, Ms Berejiklian may ease rules, including the maximum of 10 visitors per household.
“I’m pleased with what we’ve seen overnight, but again, it’s volatile,” she said.
“If we see the trend continue in the next few days, obviously that will give us more confidence to look at Thursday and Friday.”
On Monday, drive-through testing clinics at Summer Hill and Rozelle had waits of up to four hours after an instance of transmission in Erskineville and health alerts for locations in the city and inner west brought thousands to testing sites.
By 2pm, testing clinics at Ashfield and Rozelle had started turning people away. Others did not make the cut at the Earlwood site when it closed at 4pm.
Health Minister Brad Hazzard strongly recommended people wear masks in all public indoor venues and on public transport across Sydney, including at grocery stores and places of worship.
He also urged businesses not to let anyone onto their premises unless they keep precise records.
Mr Hazzard warned people who had been providing false names and phone numbers to venues must stop, saying individuals who had been calling themselves Donald Duck or Mickey Mouse were “as stupid as it gets”.
As states and territories increasingly cut off access for Sydneysiders, Ms Berejiklian urged her counterparts to consider the heartbreak border closures would cause ahead of Christmas.
“Let’s all of us make our decision on the facts,” she said. “Consider that it is a very emotional time of year … please make sure your response is proportionate to what is happening,” she said.
Prime Minister Scott Morrison said he understood this situation so close to Christmas was frustrating, but NSW was managing the outbreak well.
“It may well be that what we’re seeing in the Avalon outbreak comes and goes the same way that the Adelaide outbreak went and it all comes and goes in that sort of period of time,” he said.
“Things can then restore to where they were prior to that … We’re not at that point yet to be able to make those judgments, so hopefully in the next few days, next week, that will become clearer.”
Queensland’s Health Minister Yvette D’Ath said the earliest the state will reopen to Greater Sydney will be January 8, depending on all community transmission cases in NSW being confirmed as linked.
NSW Deputy Premier John Barilaro urged people to get tested before visiting the regions and to consider delaying their travel until the cluster is brought under control.
Mr Barilaro also asked northern beaches residents who were in regional NSW when the lockdown came into force to self-isolate.
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Kate Aubusson is Health Editor of The Sydney Morning Herald.
Mary Ward is a health reporter at The Sydney Morning Herald.