From Jan. 8, China will scrap all quarantine measures for Covid-19, including requirements for inbound visitors, both foreigners and Chinese nationals, according to the National Health Commission.

The commission late Monday issued a plan to stop treating Covid-19 as a “Class A” infectious disease, which calls for stringent control measures, and downgrade the management of the virus to “Class B,” which requires more basic treatment and prevention. The Wall Street Journal reported last month that China was weighing such a move, which would give it room to further loosen public-health measures.

The change means people traveling to China from abroad will need to have only a negative Covid-19 test within 48 hours to be allowed into the country, the NHC said. International arrivals will no longer be required to be tested on arrival or undergo quarantine—a major step toward opening up for a country that has been largely closed off to the outside world for three years.

The commission in its statement pledged to facilitate foreigners’ visits to China, including those for business, studying and family reunions, and to provide visa assistance.

The shift came as fever clinics and hospital emergency rooms in Beijing continued to overflow with patients on Monday and Chinese leader

Xi Jinping

called on local officials to take pains to save lives.

Before Monday’s loosening of Covid restrictions, Mr. Xi addressed his country’s new pandemic reality for the first time in comments marking the 70th anniversary of the Patriotic Health Movement, a campaign to wipe out flies and mosquitoes launched by

Mao Zedong

during the Korean War to fortify China against the possibility of American germ warfare.

“At present, our country’s Covid prevention and control efforts are facing new circumstances and a new mission,” Mr. Xi said. China should launch “a more targeted Patriotic Health Movement” to “effectively guarantee the lives and health of the people.”

Visits to three major hospitals in Beijing by the Journal on Monday showed the capital’s healthcare system still swamped with an influx of patients following the government’s about-face on Covid-19 controls, which has left many citizens, especially the elderly, scrambling to find treatment.

In the emergency room of eastern Beijing’s Chaoyang Hospital, known for treating respiratory diseases, hallways at the intensive-care unit were packed with dozens of elderly patients lying on portable beds. One nurse said all the ICU beds were full and only patients with the most life-threatening symptoms were being admitted. “Those patients with less severe symptoms can only get a temporary bed and stay in the hallway,” she said.

On Monday, the Chinese Center for Disease Control and Prevention issued a report showing fewer than 2,700 new infections and no new deaths on Christmas Day. Over the weekend, local officials presented a much grimmer picture. 

A senior health official in the coastal province of Zhejiang, home to e-commerce giant

Alibaba Group Holding Ltd.

, said on Sunday that new daily infections had topped one million, with the wave expected to peak at around two million cases around New Year’s Day.

Roughly half a million people were being infected every day in the northeastern city of Qingdao, a local health official said in a since-removed interview with a state-owned broadcaster.

To minimize the impact of the infection surge on China’s already battered economy, some cities said people could return to work even if they had mild symptoms. Authorities in Shanghai said Saturday that the city’s 25 million residents wouldn’t need to be isolated at home for more than seven days, even if they are still testing positive.

Rapid transmission of Covid-19 in China raises the likelihood for fresh outbreaks beyond its borders and the emergence of risky virus variants, said

Michael Osterholm,

director of the Center for Infectious Disease Research and Policy at the University of Minnesota.

“New variants are a huge possibility, and they could have a tremendous impact on the rest of the world,” Dr. Osterholm said.

In his own comments marking the anniversary of the Patriotic Health Campaign, which evolved over the years to target infectious diseases such as malaria, China’s Premier

Li Keqiang

said adjustments to the country’s Covid-19 policies were being implemented in an orderly manner, but urged officials at every level of government to address public demands for medical care and supplies.

China’s health system, thinly resourced even before the pandemic, has struggled to contend with the fast-spreading Omicron variant. The growth in infections has sent people scrambling to buy up home test kits along with ibuprofen and other medications.

At Chaoyang Hospital’s emergency room on Monday, digital screens showed a long wait list for people seeking treatment at the internal-medicine department. In an interview last week with China’s state broadcaster, Mei Xue, deputy director of the hospital’s emergency department, said around 400 patients were coming seeking internal medicine treatment every day—roughly four times the normal number.

“These patients are all elderly people with underlying diseases. After the combination of fever and respiratory infection, they are all very seriously ill,” he said.

A staffer with Beijing’s emergency medical center, which coordinates requests for urgent medical care in the city, said he and his colleagues had been working nonstop to transfer patients to Chaoyang Hospital in recent weeks and he expected the current situation to last for a few more weeks.

To cope with the surge in patients, the hospital has opened a second fever clinic in a nearby sports stadium for Covid-19 patients with mild symptoms.

Peking Union Medical College Hospital and Peking University First Hospital, both located in the center of Beijing, were similarly overwhelmed.

A sign outside the Peking Union emergency room warned patients it could take more than four hours to see a doctor. A nurse at Peking Union’s fever clinic said that for weeks patients had been forced to wait in the hallways for beds to open up. One elderly patient, unable to secure a bed, was lying on a metal bench just inside the entrance of the fever clinic.

A nurse at Peking University First Hospital’s emergency room said beds there were all full and the wait time at the internal medicine department was roughly six hours. The hospital public address system announced that nearly 50 patients were waiting to be seen.

In recent weeks, doctors and nurses from around China have been dispatched to Beijing to support the capital. Shandong province sent a team of medical staff to Beijing, according to state media reports.

In the U.S., the State Department on Friday updated its travel advisory and is asking that people reconsider travel to China due to the surge in Covid-19 cases, arbitrary enforcement of local laws and Covid-19-related restrictions.

—Xiao Xiao and Dominique Mosbergen contributed to this article.