Though Sydney has been in lockdown for nearly two months now, the curbs are generally looser than those that helped Melbourne beat back the virus last year; daily cases have surged from 12 on June 26, when the stay-at-home order was first announced, to records of around 350 this week.
The situation is putting Australia in the worst of both worlds: half the population of 26 million people are cooped up again, but the delta variant is still spreading to new cities and regions hundreds of miles away, just like it is in reopened economies like the U.S. and U.K. National capital Canberra on Thursday became the latest to order a lockdown after one case were found.
New South Wales Premier Gladys Berejiklian is now under increasing pressure from other regional leaders and some health experts to tighten social-distancing restrictions to stem the outbreak, as her playbook of keeping the economy relatively open while trying to contain delta's spread appears to be unequal to the variant's highly contagious nature. While residents of Sydney and other locked-down areas have been told not to leave home unless unavoidable, there's a lengthy list of exemptions such as for outside exercise or essential work that some people are using liberally.
"Covid Zero is clearly not holding up under delta -- it's so much more contagious," said Raina MacIntyre, a professor of global biosecurity at the University of New South Wales. Unless Berejiklian changes tactics, "it will keep spreading and the case numbers will keep rising, and it will pose a greater threat to the rest of Australia."
MacIntyre said the only way to get Sydney's outbreak under control was to enforce city-wide night-time curfews, curtail the number of retailers allowed to open, and circle the city in a "ring of steel" to ensure residents can't leave -- as occurred in Melbourne last year during one of the world's most stringent and longest lockdowns.
It's a dilemma also facing other countries with a zero-tolerance approach to Covid-19, including China and Singapore. With delta being so much more transmissible than the original virus, these governments need to ramp up the strictness of their containment measures to slow down spread, even as populations fatigue from the 18 months of stop-start lockdowns.
The slow nationwide vaccine rollout is the biggest obstacle in the way of Australia's path to normalization and international reopening after shutting its borders in early 2020. Only 36.2% of people have received a first dose, one of the lowest levels among developed economies, according to Bloomberg's vaccine tracker.
There's also concern the decision to tier the outbreak response in different parts of Sydney is causing social unrest. Some areas of its south and western districts hardest hit by the outbreak -- which also have relatively large multicultural populations and wider socio-economic problems -- have been dealt stricter travel restrictions than those in the more affluent eastern and northern suburbs.
Mistrust of authorities has been fueled by military patrols in those areas aimed at supporting the police in enforcing lockdown rules.
Berejiklian has been criticized by health experts who say she didn't enforce Sydney's lockdown early enough after delta was initially seeded in the community in mid-June by a limousine driver who came into contact with infected international flight crew. Still, the state premier insists the lockdown measures are the toughest implemented in Australia, and the outbreak's spread is due to delta's virulence and non-compliance by a minority of residents.
The dangers of relying on people to self-police given high levels of lockdown fatigue was evident in a high-profile case of an infected Sydney man who traveled almost 500 miles to look at real estate. He did not use his phone to "check in" at venues he visited as required, and the tourist hub of Byron Bay and other towns he visited were this week locked down as a result.
"Many smaller cities are now in lockdown, with all the economic and emotional issues that come with that," said Sanjaya Senanayake, an infectious diseases specialist at the Australian National University Medical School. "That could have been avoided if those people simply hadn't left Sydney, the center of the outbreak. It only takes a small minority of people to be non-compliant to cause a lot of damage."
Other state leaders, who have implemented their own hard borders against Sydney residents, are losing patience with Berejiklian, saying the deteriorating situation in New South Wales is threatening their own Covid Zero strategies that have so far kept coronavirus deaths in Australia to below 1,000.
Earlier this week, Victoria state Premier Daniel Andrews urged Berejiklian to build a "ring of steel" enforced by police around Sydney, even as he battles another outbreak in Melbourne that's placed the nation's second-largest city in lockdown for a sixth time.
Western Australia state Premier Mark McGowan -- perhaps the nation's strictest adherent to the zero tolerance approach -- told reporters on Wednesday that New South Wales authorities "don't have the backbone to do what is required."
Meanwhile Berejiklian, who hasn't ruled out tightening some of Sydney's rules, is now backing away from indicating that she could ease restrictions by the end of the month should case numbers fall and her state's adult vaccination number reaches 6 million. It's at about 4.7 million now.
While Prime Minister Scott Morrison is promising every adult will have access to a vaccine by the end of the year, he said on Thursday that there are no other options in the meantime but to enforce strict stay-at-home orders where necessary.
"Suppress and vaccinate -- that is the phase we are in," Morrison told parliament in Canberra, just hours before the city entered its first lockdown for more than a year. "Whether in Europe, the Netherlands or Singapore or Japan or other countries: where they have sought to open up, the delta variant has had a very different view."