Passengers wearing sanitary masks wheeled their luggage through lines that stretched across most of the airport lobby. As the clock ticked toward 10 a.m. local time, people crowded the doors of train stations, unsuccessfully attempting to get inside.

That was the scene on Thursday morning in Wuhan, the central Chinese city of 11 million people where coronavirus broke out last month. State-run media reported hours earlier that no one would be allowed to leave the city for an undetermined length of time in an effort to contain the pneumonialike illness that health authorities say has killed at least 17 people. Train stations, ferries, buses and the airport all have shut down.

The scale and complexity of Wuhan’s quarantine is probably unprecedented, said Howard Markel, a professor of history and medicine at the University of Michigan.

“This is just mind-boggling,” he said. “I’ve never read about or seen a bigger one than they’re proposing.”

The quarantine comes at a troublesome time for the roughly 400 million people who are traveling in China for the Lunar New Year festival, which begins Saturday. Almost 25 million passengers were expected to travel through the three main stations of China Railway’s Wuhan branch, and the number of flights to and from the airport were expected to increase from 600 to 800 each day.

Even before the quarantine, authorities had required people to wear medical masks in public places. Many stores had sold out on Wednesday.

No government has ever shut down a city of Wuhan’s size, so there’s no road map for Chinese officials, Markel said. But in addition to closing transportation hubs, he said a quarantine of that magnitude will probably mean shutting down the city’s port and its roads leading in and out.

The government also will have to arrange for special transit to bring in food, water and medicine, while hospitals will need to prepare their doctors and nurses to provide in-home care. Morale will also be key, Markel said. If officials are smart, he said, they will ensure residents have ready access to video streaming and other online entertainment.

Markel said the quarantine signals how seriously China is taking the outbreak: “It’s a bazooka, not a BB gun.”

Pressure from the international business community, which has a huge economic stake in China, is probably partly responsible for the country’s sweeping response, Markel said. Another factor is history. During the deadly outbreak of severe acute respiratory syndrome, or SARS, in the early 2000s, the Chinese government took months to publicize its earliest cases. This time, Markel said, officials want to send a different message.

Now, as then, battling the outbreak is going to be costly. SARS cost about $40 billion, Markel estimated. Depending on how far it spreads, he said, coronavirus could cost more.

In the eyes of some public health experts, the quarantine could also cost time trying to contain the virus. Jennifer Nuzzo, a senior scholar at the Johns Hopkins Center for Health Security, said that people fleeing Wuhan to escape the restrictions makes it hard for authorities to track where the virus may have spread. People who experience symptoms may also hesitate to come forward because of the government’s extreme measures to control the illness, she said.

Quarantines are often imposed for the incubation period of a disease, or the amount of time from exposure to the appearance of symptoms. For coronavirus, Nuzzo said, that’s 14 days. She said trying to contain a major city for that long is likely to lead to backlash.

“I frankly don’t see how they’re going to be able to pull something like that off,” Nuzzo said.

Past efforts at large-scale quarantines have been largely unsuccessful. Nurses had to tend to the every need of health-care workers who were quarantined in Taiwan during the SARS outbreak, using a tremendous amount of resources, Nuzzo said. A quarantine in Liberia during the Ebola outbreak in 2014 resulted in mass upheaval, and the government quickly pivoted to a milder approach, Nuzzo said.

In Wuhan on Thursday, flight-tracking websites showed dozens of canceled flights out of Wuhan Tianhe International Airport, which usually offers routes to New York, London and Rome, among other major cities. It is also one of China’s busiest airports for domestic flights.

Travelers also were thwarted at train stations, where locked doors kept them outside.

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