Beijing reopens a mass isolation center as it tries to avoid a citywide lockdown.

The authorities in Beijing on Monday said that they had reopened a mass coronavirus isolation center, the latest in a raft of measures to try to stave off a citywide lockdown.

While Beijing has recorded only 400 cases since April 22, the move to start using the Xiaotangshan hospital, which has more than 1,000 beds, appears to be aimed at avoiding the fate of Shanghai, which is still under lockdown. The hospital was built in seven days in 2003 to treat patients of the SARS epidemic and was used again in 2020 to treat Covid-19 patients.

Officials in Beijing are under immense pressure to quickly stamp out outbreaks. In recent days, they have placed a temporary ban on dining in restaurants, closed schools indefinitely and ordered residents to show proof of a negative test within the past week to enter public spaces, including public transportation.

Universal Beijing Resort, one of the city’s major tourist attractions, was also ordered shut just as the five-day May Day holiday started on Saturday. And nearly all of the Chinese capital’s 22 million residents have undergone three rounds of testing.

So far, the scale of the outbreak appears to be limited. On Monday, officials announced 50 new cases down from the 59 reported on Sunday. At a news conference on Sunday, health officials said that they had successfully sequenced dozens of cases and established clear chains of transmission.

By acting early, officials in Beijing are hoping to avoid a punishing lockdown similar to the one in Shanghai during the past month. Since the beginning of March, Shanghai has reported more than 550,000 cases, leading officials to institute harsh quarantine measures that have resulted in shortages of food and supplies as well as protests.

Cases in Shanghai are now falling. On Monday, the authorities reported about 6,600 new infections, down from 7,800 the day before. In recent days, the local government has shuttered several mass quarantine sites that had been used to house patients.

Concerns remain about China’s population of older adults, who have emerged as one of the most vulnerable groups during the pandemic. Just over half of people 80 and older have had two shots, and less than 20 percent of that age group have received a booster, Zeng Yixin, a vice minister of the National Health Commission, said in March.

Over the weekend, the authorities were put on alert after several videos were widely shared on Chinese social media showing workers in protective suits unzipping a body bag and wheeling it back into a home for the care of older adults in Shanghai. On Monday, local officials confirmed that a person had been put into a body bag while still alive, according to Chinese state media. The officials added that the person had since been transferred to a hospital and was showing stable vital signs.

Chinese state media later reported that four people had been dismissed from their posts in connection with the incident, including two local officials overseeing care for older adults and the director of the nursing home.