"We always should have gone for zero, and we were very successful," Andrews told the waiting media pack. "You have to give accolades to states for achieving that, but that isn't going to continue any more. Now we have to work on reducing our risk."

It was a particularly stark message from a Premier whose experiences in 2020 had taught him to act strongly and quickly.

A week earlier his NSW counterpart Gladys Berejiklian, criticised for having taken what was seen to be a more cavalier approach, had told 7.30 host Leigh Sales the Delta variant rendered a zero-COVID target "completely unrealistic". It was now time to learn to live with the virus, she said.

The outbreaks, starting at different times, had simmered along with low daily case numbers before a sudden surge around a month in. Meanwhile, a month after Victoria and two months after NSW, the virus jumped the ACT border.

Comparing one outbreak to another and attempting to overlay their trajectories is a rough science at best. But as the ACT outbreak hits the mark where both NSW and Victoria started to escalate, the territory finds itself at a fork in the road.

Its lockdown has been similar to Victoria's. Our daily case numbers have been similar, too. Are we bound for a similar fate?

Deakin University epidemiology chair Catherine Bennett warns the next seven days will prove vital in shaping the outbreak's trajectory, as the city holds its breath to see which way numbers go. But she is confident the capital is not on the same path as Australia's two biggest states.

"If you get through this next week, and this pattern of 13 to 15 [daily cases] holds, you're probably not going to see it take off," she says.

"It's something to watch out for now, and make sure everyone's aware that it's a risky time.

"There could be virus out there. But if we can get through the next weeks with everyone testing and finding no more virus, we're looking good."

Crucially, the ACT has not uncovered any major secondary outbreaks, as was seen in NSW and Victoria by this point. Bennett says the acceleration in Sydney was driven by clusters popping up in the city's west, unable to be linked to each other or the original outbreak, which acted as a "second launch" weeks later.

"That tells you you've got a more mature outbreak, which has been running sight-unseen for a few generations of spread," she says.

"[But] it's looking promising [in the ACT]. You're now well into the period where both Sydney and Melbourne found these secondary suburban outbreaks."

Bennett says the Delta strain can only stay under the radar for a couple of weeks before symptomatic cases emerge.

"That said, you've got to hold your breath over the next few days. If there've been other chains of transmission that have been missed, the Health Department might find a case, then test around them and find 15," she says.

"It's not over yet. It's still that time where if anyone's got symptoms, you really want to encourage them to get tested."

Bennett says the ACT's month-long lockdown extension could be cut short if testing remains high and case numbers stay flat.

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The ACT government has lauded Canberrans for their compliance and, as one of the least COVID-impacted jurisdictions in Australia over the past year and a half, pandemic fatigue is less of an issue. Bennett accepts adherence has faded in Victoria during its latest lockdown, but says it is difficult to assess the impact of this on spread.

"There's definitely a sense of less attention to the all the rules for some people ... and probably also a sense of how those things are being enforced by the police. That then becomes cyclical," she says.

The ACT's effective reproductive rate - the number of people an infected person passes the virus on to - has hovered below 1.0 in the last week. University of South Australia biostatistics expert Adrian Esterman says comparing its outbreak with Victoria, where the rate remains at 1.3, is "chalk and cheese".

"It's really a tale of three states. We've got the ACT, which is grumbling along at a very low number of cases. It's not increasing, though [the trend] could potentially be going down a bit," he says.

"Then you've got NSW, which had the most massive outbreak ... But now they've got a huge percentage of their population in comparison to other states and territories vaccinated, we're starting to see numbers coming down.

"Now Victoria is starting to see a slowing down as well ... Their vaccination is way behind NSW, but there's still a glimmer of numbers slowing down in Victoria."

The ACT's lockdown came after more than a year without a COVID-19 case. But Victoria's latest lockdown, its sixth, came just a week after it exited its fifth.

Esterman describes the decision as a "big mistake", made while the virus was still circulating. Unlike the ACT, he says the situation in Melbourne was exacerbated by community apathy - as well as a 4000-strong anti-lockdown protest in August.

"You can almost guarantee there would have been some infected people among them, and even potentially some super-spreaders," he says.

Andrews' abandonment of COVID-zero was an acceptance the state had nothing left to throw at Delta, and could only slow the spread as vaccination rates limped upwards.

But with Canberrans able to picnic in groups of five and in-person house inspections returning, Esterman says the territory has extra levers to pull.

"A little bit more effort from the ACT and they could almost definitely get it down to zero [eventually]. But that's if they want to; we've seen NSW wasn't interested in doing that," he says.

But the ACT government knows quashing its own outbreak is no guarantee of a COVID-free future.

Chief Minister Andrew Barr is warning Australia's hospital capacity "looks quite scary" as NSW pushes ahead with plans to ease restrictions at 70 per cent vaccination.

"The modelling indicates case numbers would go from thousands into the tens-of-thousands each day," he says.

Barr claims a "very challenging" peak could occur around Christmas - NSW says October - with the ACT bracing for an influx of NSW patients.

Imogen Mitchell, clinical director of the ACT's COVID-19 response, describes modelling as a "variable feast" - and warns there is no way of predicting exactly how much strain will be placed on the territory's system. Slight tweaks - vaccination status, restrictions, patient ages - "massively change what you're dealing with".

Mitchell, who has held the role since March 2020, says the public system is currently funded to care for 28 intensive care patients, complemented by surge capacity in private hospitals. She says the next month is critical in ramping up vaccination.

"There's no doubt there is a significant flow-on effect from NSW opening in a greater way," she says.

"Some of the numbers that have been generated out of the modelling are extremely concerning ... But the difficulty is it's impossible to predict until it really does happen."

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Mitchell warns the ACT's isolation - the territory is 300 kilometres from the nearest tertiary intensive care unit - makes it particularly vulnerable. It means extra steps to protect the healthcare workforce may be necessary, including visit limits - a move she appreciates can be "extremely disturbing" - and finding ways to avoid staff being furloughed.

"That might mean we need to respond differently in terms of public health measures," she says.

ACT Health's catchment area covers around 240,000 NSW residents - the numbers vary depending on type of treatment - who typically account for about one-quarter of its hospital patients. Mitchell says that number is higher in intensive care.

"[But] a lot of people retire from Canberra to the South Coast. So in part they're really part of our greater families ... We certainly haven't differentiated. For me, a patient is a patient," she says.

Barr claims Berejiklian has personally assured him NSW patients will not require intensive care in the ACT. Berejiklian's office declined to comment when asked to confirm the conversation.

Canberra's shift from a "short, sharp" lockdown to rolling extensions has prompted fears compliance could fray. Hopelessness sets in as short-term targets stretch on indefinitely, the argument goes.

But UNSW infectious disease social scientist Holly Seale says there is little evidence to suggest frustrations over ongoing restrictions cause widespread non-compliance.

Seale says people's perception of the risk posed by COVID-19 most affects their behaviour, with high transmission and death enough to ensure adherence to the rules. Canberrans growing disgruntled only need to look across the border, she says.

"I'm sure we've all voiced at one point that having to having to walk and stay in the local area can be frustrating," she says.

"But then it's that balance between voicing that and it actually influencing whether or not we comply.

"It's hard, but what do we see then as the the possible next steps if we don't comply right now? Well, it's exactly what Sydney and Melbourne are going through."

The ACT started well ahead in terms of vaccines; nearly one-quarter of its total population (22.5 per cent) had received both doses by August 12, well ahead of Victoria on July 13 (9.9 per cent), and NSW on June 6 (2 per cent). First-dose coverage was also higher: 41.9 per cent in the ACT, compared to 9.9 per cent in Victoria, and 18 per cent in NSW.

Rates have since soared in NSW and Victoria, but remain slower in Queensland and Western Australia, where Delta is yet to grow roots. Rather than prompting non-compliance, Seale says the lockdown extensions may simply boost vaccine uptake.

"If people think the hook to getting the territory into the next phase is to get the vaccine rates up, that may then nudge people to [do so] ... They think: if this is going to continue to be pushed back, then let's do something about it," she says.

But while the ACT enjoys the highest full-vaccination rate in Australia, it may find itself hostage to slower rates elsewhere. The national reopening plan requires the national average to reach 70 per cent to trigger the first tranche of easing in jurisdictions above that rate, before further easing at 80 per cent.

While Barr expects to be 10 per cent ahead of the nation at both trigger-points, the latest update from Operation COVID Shield warns Australia may be cutting it fine to reach 80 per cent coverage by Christmas.

"Getting people to understand what Christmas could be if we get there is a carrot," Seale says.

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