The timing of Sydney's Croydon coronavirus cluster five days, or one average incubation period, after Christmas begs an uncomfortable question.
The city enjoyed a slight three-day easing of COVID-19 restrictions despite the virus circulating on the northern beaches.
So did Christmas Day cause the Croydon cluster and is Sydney now paying the price?
Chief Health Officer Kerry Chant did not hesitate on Wednesday before shutting down the suggestion.
Six members of an extended family who've tested positive for the virus had taken part in "a series of events", Dr Chant said.
Health authorities and contact tracers have identified more than 30 close contacts of the family and are now racing to understand "sequential gatherings" across multiple days where COVID was likely being passed.
"Clearly, it's premature to say that it was on one day," Dr Chant said.
"But we are investigating a number of lines of inquiry to understand that transmission event.
Dr Chant highlighted that indoor, household events remain the highest risk for COVID transmission, as the Croydon cluster illustrates.
She also foreshadowed more cases would be associated with the extended family and expressed concern that, so far, no link to the northern beaches cluster had been found.
Epidemiologist Mary-Louise McLaws believes the Croydon cases represent a third generation of the northern beaches outbreak.
She believes that from an outbreak management perspective, Christmas should not have gone ahead as it did.
"We'll still see some more cases potentially because of Christmas," Professor McLaws said.
"Then we have New Year and then cricket."
Sydney will host the third Test match between Australia and India on January 7, despite the ongoing coronavirus outbreaks.
Premier Gladys Berejiklian referred to the Croydon cluster, as well as cases in Wollongong, as "the proliferation of cases outside the northern beaches".
Full lockdown warranted, experts warn
While restrictions have been slightly tightened for New Year's Eve, the developments have also reignited debate about whether a full-blown lockdown is warranted.
The ABC's Norman Swan believes if NSW is to act based on the "precautionary principle", now is the time to lock down Greater Sydney for a fortnight.
"You've now got this virus seeded throughout Greater Sydney, you've got a problem in Wollongong, the numbers will go up and down," he said.
"It's one incubation period after Christmas, so you'd expect a spike around about now — and that's a springboard for New Year's Eve as well."
Dr Swan said modelling from the University of Sydney's professor Mikhail Prokopenko showed every day a lockdown was delayed represented a full week at the other end of the outbreak, in terms of getting the cases under control.
He said masks should also be mandated and the experiences in Victoria, as well as overseas in Israel, the UK and US, showed "half-hearted measures" did not work.
"We've been relying in NSW on the absolutely fantastic work of contact tracers," he said.
"It is truly amazing … but it won't take long for that to be overwhelmed."
