BEIJING (BLOOMBERG) - China is facing its toughest virus battle since the first days of the pandemic. Rather than pivot from the strict Covid-19-zero route that others have abandoned, the country is doubling down, despite rising costs to its people and economy.
The current resurgence already accounts for the most infections and the most days with new cases spurred by the Delta variant since May. It is also the most widespread outbreak since China first vanquished the infection that was first reported to have emerged in Wuhan two years ago.
Despite ever more extreme measures aimed at shutting it down - from testing an infant more than 70 times to locking down Shanghai Disneyland on one case - the pathogen is proving harder than ever to wipe out.
A time series of local infections compiled by Bloomberg News shows the country's success in cutting off transmission over the pandemic's first 18 months.
There was not a single locally acquired case for about one-third of that period, with zero infections recorded on 177 of the past 540 days.
That compares with an average of about 85,000 cases every day in the United States, even though China's population is four times as large.
But those victories are increasingly fewer, and further apart. The faster-spreading Delta strain got through strict mitigation measures including weeks-long quarantines and border curbs during the summer and fall.
That creates a new challenge as the world's most populous country heads into winter, when a tougher viral cycle will meet travel surges tied to holidays like the Chinese New Year, in February.
The initial success and political capital that have resulted from China's strategy of bringing cases back to zero has hardened Beijing's resolve, even after the arrival of the insidious Delta variant, the now dominant Covid-19 strain that incubates more quickly and penetrates defences more easily.
Other early Covid-19-zero proponents like Australia and Singapore deemed it too costly to continue pursuing elimination, leaving China to grind largely alone on the global stage.
The decision by most of the world to learn to live with the virus and the recent rise in cases make it a precarious time for China.
"The outbreaks in China's neighbours and around the world remain elevated, creating a complicated and grave challenge for this winter and next spring," said Dr Wu Liangyou, an official with China's National Health Commission, at a briefing in Beijing earlier this month explaining why the country cannot let down its defences.
It has not been easy. Even after five weeks of intense battle against infections across the country, there are still a handful of new local cases every day.
The approach has won praise within China, where residents have little to fear from a virus that's killed more than 5 million people worldwide. While Covid was first detected in the country, fewer than 5,000 people there have died from it.
"Let's focus on the result," Dr Liang Wannian, an epidemiologist who is leading China's special task force on the Covid-19 response, told state broadcaster CCTV in a recent interview. "First, we can quickly extinguish a ferocious outbreak and reduce death and severe disease to a minimum. Everybody can see that. Second, our economy is not impacted by the measures and strategy we took."
Easing prematurely could undo the hard-earned achievement, impact the economy and overwhelm the medical system, he said.
But keeping Covid-19 out requires China to be ever-vigilant, and there are signs that the increasingly strict measures are weighing on certain parts of the economy.
The latest outbreak emerged from a small flare-up among tourists visiting the scenic north-west, then quickly engulfed two-thirds of the mainland's 31 provinces.
The local authorities ordered lockdowns, blitz-tested everyone in cities that had cases and quarantined close contacts, only to see infections grow further and pop up elsewhere.
The surge triggered intense implementation of the country's Covid-19 containment tactics. One county turned all its traffic lights red to stop people from going out. Shanghai Disneyland quietly closed its gates on Halloween night while medical staff poured in to swab tens of thousands of guests for Covid-19 before they could leave.
Cities expanded the criteria for contact tracing, ensnaring people nearly a kilometre away from someone with a diagnosed infection. A town on the border with Myanmar built a Covid-19 wall to keep cases out.
Aggressive containment is likely to inhibit consumption and contribute to an economic slowdown driven by the energy shortage and a crackdown on debt- property expansion, said Dr Wang Tao, chief China economist at UBS.
Covid-19 curbs are crippling the travel and services sector, she said. The country's economic growth could slow to 4 per cent next year, down from the current projection of 5.4 per cent that is already a decline from this year, if Covid-19 curbs are extended after the Winter Olympics in Beijing in February, she said.
One thing is clear: keeping Covid-19 out is not going to get easier.
"I don't think it's a reasonable goal to get to zero," said Dr Jason Wang, director of the Centre for Policy, Outcomes and Prevention at Stanford University. "This Covid-19-zero approach, particularly with variants, is just very difficult to do."