NEW YORK (NYTIMES) - In the battle against the coronavirus, few places seemed as confident of victory as China.
The country of 1.4 billion people had eradicated the virus so quickly that it was one of the first in the world to open up in spring last year. People removed their masks and gathered for pool parties.
In recent months, the government has contended with sporadic outbreaks in various provinces, but stamped them out swiftly by mobilising thousands of people to test and trace infections, as well as locking down communities.
That model is now looking increasingly fragile.
China is facing its biggest challenge since the virus first erupted in the Chinese city of Wuhan last year: The highly transmissible Delta variant that is rapidly spreading throughout the country.
Chinese officials have acknowledged that curbing this outbreak will be much harder than the others, owing to the fast and asymptomatic spread of the variant.
While the number of cases are still relatively low compared with the United States and elsewhere, these new outbreaks - happening in cities such as Nanjing, Wuhan, Yangzhou and Zhangjiajie - are showcasing the limitations of China's zero-tolerance approach to Covid-19. They may also undermine the ruling Communist Party's argument that its style has been an unquestionable success in the pandemic.
Although the government had to stamp out a Delta flare-up in June in Guangdong province, the authorities this time are dealing with a much larger spread.
Since the current Delta outbreak started on July 21, the number of cases has risen to 483, more than the sum total of infections from the first five months of the year. By Tuesday (Aug 3) afternoon, the virus had spread to 15 of the 31 provinces and autonomous regions in China.
"Once it reaches so many provinces, it's very hard to mitigate," said Yale University's associate professor of public health Chen Xi. "I think this would be surprising and shocking to the rest of the world. Such a powerful government has been breached by Delta. This will be a very important lesson - we cannot let our guard down."
Last week, Ms Sun Chunlan, a vice-premier of China, blamed "ideological laxity" for the Delta outbreaks and urged officials to step up their prevention efforts. "We cannot relax for a moment," Ms Sun said.
Some public health experts in the country say it is time for China to rethink its Covid-19 strategy. In a recent essay, Dr Zhang Wenhong, who advises the Chinese government on dealing with Covid-19, floated the idea of following a model similar to that of Israel and Britain, in which vaccination rates are high and people are willing to live with infections.
For now, China has stuck to the same strict playbook. Across the country, the government has instructed people not to travel unless necessary.
In the cities of Zhangjiajie and Zhuzhou, 5.4 million people have been barred from leaving their homes. Roughly 13 million residents in the city of Zhengzhou, the site of deadly floods in July, had to stand in line for virus testing starting last weekend.
In Nanjing, where the recent Delta cases first appeared, millions of residents have had to participate in four rounds of testing.
"It's just torturing the masses," said Ms Jiang Ruoling, a resident in Nanjing, who has been tested four times in the last three weeks. Ms Jiang, who works in real estate, said she understood the need for testing, but was still critical of officials for failing to control the latest outbreak. "The leaders are actually wasting resources and everyone's time," she said.
Dr Yanzhong Huang, a senior fellow for global health at the Council on Foreign Relations in the US, said China's containment-based strategy would not work in the long run, particularly as new variants continue to emerge.
"It will become extremely costly to sustain such an approach," he said.
And yet, China appears unwilling to take any chances. In Wuhan, the authorities on Tuesday started testing all 12 million residents after only three cases of the Delta variant were discovered. The cities of Sanmenxia and Zhuhai have also begun mass testing. In Beijing, where there are five infections, train service from 23 cities has been cancelled.
Dr Jennifer Huang Bouey, a senior China policy expert and an epidemiologist at the Rand Corp, said that even with strict controls, it may not be realistic for officials in China to get these latest cases down to zero. "I think they may have to prepare people for a higher tolerance of Covid-19," Dr Huang said.
Part of the challenge for Beijing is that the Chinese-made vaccines being used to immunise the country are not as effective against the Delta variant as other shots. The government says it has already administered about 1.69 billion doses. Health officials are now considering giving booster shots to people with compromised immune systems as well as older citizens.
Dr Zhong Nanshan, a top epidemiologist, said China's vaccines are 100 per cent protective against severe disease caused by Delta, and 63.2 per cent effective against asymptomatic cases. He said he was confident that the latest outbreak would be controlled in about 10 to 14 days, during which officials hope to carry out extensive contact tracing in Nanjing and several other cities in Jiangsu province.
The current Delta cases have been linked to a flight from Moscow that landed in Nanjing on July 10. Seven passengers on the flight were infected with the variant. On July 20, nine airport cleaners tested positive. Their infections spread quickly among people who entered the airport, a major transportation hub.
A mother and daughter as well as a 12-year-old girl who flew to Zhangjiajie after transiting for two hours in the Nanjing airport have all tested positive. Three other tourists who travelled to Zhangjiajie have been linked to an outbreak in the central city of Changde, after they all took a river cruise. About 27 infections in at least six places have been linked to the boat ride.