WUHAN, China >> Chinese authorities drastically strengthened their coronavirus lockdown today in a desperate move to contain the deadly scourge of infections, ordering house-to-house searches, rounding up the sick and warehousing them in a convention center and other buildings converted into makeshift quarantine internment camps.

The seemingly improvised steps were announced by the top official leading the response to the outbreak as she visited the central Chinese city of Wuhan, the epicenter. They clearly signaled the ruling Communist Party’s alarm that it had failed to gain control of the coronavirus epidemic, which has overwhelmed the Chinese health care system, spread abroad and threatened to paralyze China, the world’s most populous country and second-largest economy.

The steps announced by the official, Vice Premier Sun Chunlan, evoked images of the emergency measures taken to combat the 1918 Spanish flu pandemic that killed 20 million people worldwide. The steps in China offered no guarantee of success.

The severity of the new restrictions also risked creating a humanitarian disaster in Wuhan, a teeming metropolis of 11 million that already has been basically shut down from the contagion that began more than a month ago.

The city and country face “wartime conditions,” Sun said during the visit. “There must be no deserters, or they will be nailed to the pillar of historical shame forever.”

She ordered medical workers to mobilize into round-the-clock shifts to visit each home in Wuhan, check the temperature of all residents and interview close contacts of any infected patients.

The new measures came two weeks after China barred people from leaving Wuhan, then expanded the restriction to cities in the central province of Hubei and now confines more than 50 million people — a containment of nearly unimaginable scope.

Yet the number of confirmed infections has doubled roughly every four days, afflicting more Chinese cities and towns, and experts have questioned whether the government’s actions are imposing undue hardship on people while doing little to slow the epidemic.

As of today, government figures showed the virus had killed at least 563 people and infected at least 28,018, and many believe those official statistics are far from complete.

Authorities have begun to direct patients in Wuhan to makeshift hospitals — including a sports stadium, an exhibition center and a building complex — that are intended to house thousands of people. Inspecting one of the centers, set up in Hongshan Stadium, Sun said that anyone requiring treatment should be rounded up, if necessary, and forced into quarantine.

“It must be cut off from the source,” she said of the virus, addressing city officials at the shelter, according to a Chinese news outlet, Modern Express. “You must keep a close eye. Don’t miss it.”

It was not clear how the already-strained facilities could handle an influx on the scale she seemed to suggest or whether the new shelters were equipped or staffed to provide even basic care to patients and protect against spreading the virus.

Photos taken inside the stadium showed narrow rows of simple beds separated only by desks and chairs typically used in classrooms. Some comments on Chinese social media compared the scenes with those from the Spanish flu pandemic, the deadliest in modern history.

China’s leader, Xi Jinping, called the epidemic “a major test of China’s system and capacity for governance” Monday. But appearing with Prime Minister Hun Sen of Cambodia two days later, Xi said the Chinese government’s efforts were “achieving positive results.”

Xi did not make a public appearance Thursday, apparently delegating the responsibility for the crisis to deputies, who all adopted the militaristic tone set by the People’s Daily this week when it described the campaign to contain the epidemic as a “people’s war.”

Even so, there were increasing signs that the restrictions on entering and leaving Hubei were slowing the resupply of medicines, protective masks and other necessities, despite pledges by Beijing and by private companies and charities that relief was en route.

“This is almost a humanitarian disaster because there are not sufficient medical supplies,” said Willy Wo-Lap Lam, an adjunct professor at the Center for China Studies at the Chinese University of Hong Kong. “The Wuhan people seem to be left high and dry by themselves.”

Many medical experts believe that the number of those infected — and those who have died — is higher than the official count. Many Wuhan residents who are unwell but unsure whether they have the disease have been forced to go from hospital to hospital on foot, only to be turned away from even being tested for the virus, let alone treated.

Others wandered around in full protective clothing or with improvised safety measures, like plastic bags on their heads. Many have resorted to self-quarantine at home, risking the spread of the virus within families and neighborhoods.

Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center in Nashville, Tennessee, said the challenges faced by Chinese health authorities just managing the crisis in Wuhan were enormous.

“When both the physical and human resources for direct medical care are stretched, you’re going to have some unfortunate events, and people will die,” he said. “You can’t manage that great a surge of patients for an extended period of time.”

But Schaffner also raised questions about the new steps, including risks to both coronavirus patients and their caregivers in makeshift quarantine shelters.

“What happens to the people who are sick?” he asked. “Do they receive care, and at what level? And can the caregivers, in the circumstances of a stadium or school auditorium, provide care effectively — and keep themselves safe?”

The epidemic has brought much of China to a virtual standstill, even far from Wuhan. Each day brings reports of more cities effectively sealed off, public events and gatherings canceled through February or beyond, and schools preparing to postpone their post-Lunar New Year reopenings.

The effect also has spilled across China’s borders, despite the government’s frenetic efforts to respond to the epidemic while publicly portraying it as a manageable crisis. Nearly 200 infections with the virus have been confirmed in about two dozen other countries and territories, and two of the patients outside China have died.

Other countries have stepped up their own efforts to quarantine patients, including those on two cruise ships. Global corporations that depend on China’s huge market and supply chains are scrambling to deal with disruptions caused by the coronavirus, acknowledging how much they have come to count on the Chinese economy.

Cathay Pacific, the international airline based in Hong Kong, asked 27,000 of its workers to take three weeks of unpaid leave, while Nintendo, the Japanese video game maker, announced it would delay shipments of its Switch game consoles.

Major chains like Apple and Starbucks have shut down hundreds of stores in China. Yum China, which operates KFC and Pizza Hut, announced that it had shut one-third of its franchises and that it could post a loss for the year “if the sales trend continues.”

In Wuhan, the first concern is the humanitarian plight of a city beginning its third week in a state of siege. The confusion caused by sweeping calls for action at the top and a chaotic situation on the ground indicated that the Chinese government had not yet gotten a handle on the crisis.

Wang Chen, a respiratory expert who is president of the Chinese Academy of Medical Sciences, said the new makeshift treatment sites had been designed to counter transmissions within households and neighborhoods.

“If a large number of patients with mild symptoms live at home or suspected patients roam around in the community, they will become the main source to spread the virus,” Wang said, according to Xinhua News Agency.

A widely shared post on Weibo, a popular social media site, said Thursday that “conditions were very poor” at the Wuhan exhibition center that has been converted into a quarantine facility. The writer, who said he had relatives in the shelter, cited power failures and problems with heating, saying people had to “shiver in their sleep.”

The post said there appeared to be shortages of staff and equipment. “Doctors and nurses were not seen to be taking note of symptoms and distributing medicine,” it said, and oxygen devices were “seriously lacking.”

With public anger simmering, the Communist Party has moved to stifle news organizations and social media platforms where criticism of the government’s initial response were for a time left uncensored online.

The China Media Project, a watchdog group in partnership with the University of Hong Kong, published a directive from the Cyberspace Administration of China, which oversees the internet, accusing several social media companies of “illegally engaging in internet news information services in epidemic-related reports.”

It said some of the country’s giants, including Sina Weibo, Tencent and ByteDance, would be placed under special supervision to ensure “a favorable online environment for winning the war for prevention and control of the coronavirus outbreak.”

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