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Hong Kong(CNN) How to contain a runaway Covid outbreak, in a city committed to keeping cases at zero?
That's the question now facing Hong Kong officials, as daily infections top 4,000, and previous fail-safe systems begin to buckle under the strain of their own uncompromising rules.
For almost two years, Hong Kong had relied on a combination of stringent quarantines and sophisticated track-and-trace efforts to isolate positive cases, keeping the city comparatively virus-free -- even as the rest of the world began to loosen restrictions.
But those measures no longer appear sufficient in the face of the latest Omicron wave, which officials have described as a "tsunami."
Hong Kong's insistence on sending all positive cases to hospital, irrespective of the severity, has led to at least one hospital being so overwhelmed it was forced to move patients on gurneys outside, lining them up in the parking lot.
Meanwhile, a raft of tightened restrictions and targeted lockdowns have led many experts and residents to question the sustainability of such an approach as the city enters the third year of the pandemic.
On Wednesday, Chinese President Xi Jinping took the unusual step of directly calling on Hong Kong officials to take "all necessary measures," according to comments published on the front pages of two Chinese state-run newspapers.
Xi's intervention has raised fears that further restrictions similar to those seen in mainland China, including a possible citywide lockdown, could soon follow.
So far, the local government has firmly ruled out such a move, suggesting it would be impractical to confine more than 7 million people to their homes. But Xi's comments make clear that Hong Kong has little choice but to adhere to China's hard-line zero-Covid strategy -- whatever the cost.
The newest wave began in January, and quickly spun out of control despite authorities' increasingly desperate efforts.
In mid-January, the government killed more than 2,500 hamsters and other small animals after a single Covid case was linked to a pet store, sparking widespread public outrage.
Days later, a housing cluster prompted the government to lock down several buildings home to thousands of people. Soon, residents began complaining of trash piling up in the hallways, and of pay cuts for those who weren't able to work during the lockdown.
In hindsight, it was an early sign of the chaos to come, and of a government unequipped for a wave of this magnitude despite having had more than two years to prepare.
To date, less than 70% of the city's population has been fully vaccinated against Covid, according to government data, and vaccination rates among the elderly remain comparatively low despite vaccines being available since February 2021.
With numbers rising, authorities reimposed a series of familiar restrictions: closing all schools; shuttering bars, gyms, salons and numerous public spaces; suspending restaurant dine-in past 6 p.m., capping public gatherings; doubling down on a citywide mask mandate; and prohibiting more than two households to mix in private.
But these measures -- part of the government's zero-Covid playbook each time a new outbreak arises -- failed to stop the surge. On Wednesday, the city reported a record 4,285 new cases. Before this wave, Hong Kong had never seen more than 200 new cases in a day.
Many of the government's rules were formed with the zero-Covid goal in mind, such as hospitalization for all those who test positive for Covid -- regardless of their condition -- mandatory tests for anybody who may have been exposed, and quarantine of close contacts.
These rules and processes may have worked when Hong Kong was only dealing with a few dozen cases at a time -- but the scale of the latest outbreak has stretched the system to breaking point.
As of Monday evening, seven of Hong Kong's 17 public hospitals had either reached or exceeded 100% inpatient bed occupancy -- leading to the makeshift outdoor wards, which could pose a problem this weekend with rain and cold temperatures expected. Long lines stretch across the city, with people waiting hours to get tested.
But rather than consider different approaches, the government -- under pressure from Beijing -- has dug its heels in, more determined than ever to contain the outbreak.
"At this moment, we still feel that (dynamic zero-Covid) is the best strategy for Hong Kong," the city's leader Carrie Lam said last week -- referring to a new label that aims to quickly suppress all outbreaks.
Even before Xi's reported instructions, the Chinese central government stepped in earlier this week -- seemingly growing impatient with Hong Kong's inability to rein in the virus itself.
China will send health experts and medical supplies to Hong Kong, and help build new quarantine and isolation facilities, officials said -- bringing to mind the temporary hospitals that were constructed and operational within weeks in Wuhan, the original epicenter of the pandemic, at the start of it all.
Lam has publicly welcomed the central government's support, admitting Tuesday that Hong Kong was struggling to cope with the exponential growth of cases. "The problem we are facing is, given the magnitude, pace and severity of this fifth wave, it has outgrown our capacity," she said.
Though Hong Kong has been aligned with Beijing in pursuing zero-Covid, it could have taken a different route -- one now playing out in a very similar city, 1,600 miles (about 2,600 kilometers) away.
Last August, Singapore -- which for years has competed with Hong Kong for the title of Asia's top international business hub -- was the first Asian country to declare it was moving away from a zero-Covid policy to living with the virus instead. It was soon followed by Australia, New Zealand, Thailand, and others.
The mood in Singapore is now drastically different than in Hong Kong. A high vaccination rate and reopened travel with two dozen countries mean daily life has more or less resumed. Though cases there are spiking as well, people are able to go to the movies, meet friends at the bar, even attend sports events and live concerts.
The few restrictions left -- like caps on social gatherings -- may soon be lifted too when the Omicron wave subsides, the health minister said Monday. "Like most Singaporeans, I am looking forward to it," he added.
But there is little of that optimism in Hong Kong, with leaders defiant even as the city's tough travel restrictions render it increasingly isolated from the world.
"With the full support of the central (Chinese) government, the government's united effort, and citizens' full support, we have to fight against this wave of the virus," Lam said on Tuesday. "Surrendering to the virus is not an option."