LOS ANGELES — This week, a group of strangers came together under a warm Southern California sun. They played ball with their children. They took jogs down tree-lined paths. They watched movies in the afternoon.
They also had their temperatures taken several times a day by medical personnel. And they are not allowed to leave the premises.
This makeshift community on a military base in Riverside, Calif., is made up of evacuees from Wuhan, the city in China that is the epicenter of the coronavirus outbreak. The 195 people, including diplomats, infants, a football player and a theme-park designer, are among Americans who have managed to leave Wuhan since a quarantine was imposed.
Now they find themselves stuck in place in the United States. The federal government on Friday imposed a 14-day quarantine, retroactive to when the plane left Wuhan. The patients were initially told they had to wait at least 72 hours for medical testing to be completed.
The group arrived in the United States on Wednesday aboard the only chartered plane the State Department has flown to carry evacuees from China. As they passed time on the March Air Reserve Base, waiting until they can be cleared to leave by medical officials, some recalled unsettling, eerie final days in Wuhan and a jarring scene as the plane finally carried them away.
“It was surreal,” said Matthew McCoy, a theme-park designer, recalling the airplane crew members in hazardous material suits tending to passengers in masks. “They were trying to keep us calm, but they had these guys covered from head to toe taking your temperature. It felt like a C.I.A. cargo plane.”
To contain the spread of the virus, which has killed more than 200 people and infected thousands, people have been quarantined on a cruise ship, in hospital wards and on an island.
Late Wednesday, hours after the plane arrived in California, a passenger tried to leave the base and was intercepted, local officials in Riverside County said. A quarantine order was issued to that passenger, a spokeswoman for the county said, because of “the unknown risks to the public should someone leave the base without undergoing a full health evaluation.”
With ample time on their hands, the passengers performed mundane tasks.
“I’m working out, watching movies, eating well,” said Jarred Evans, 27, a football player from New York City who has been living in Wuhan for two years, where he plays for the Chinese National Football League champions, the Wuhan Berserkers. He has also been through numerous checks. “I’ve never had my temperature taken so many times in my life,” he said.
From his room at an inn on the military base, Mr. McCoy said, “It’s not Club Med, but we’re fortunate to be here. I try to stay busy with my work, social media and my hotel workout regimen.” The Spanish-style hotel, which boasts stucco archways and a large courtyard, faces a verdant lawn.
After a stopover in Anchorage for refueling and medical screening, the passengers were greeted in California by experts from the Centers for Disease Control and Prevention who conducted medical tests and offered psychological counseling. Noses and throats were swabbed. Blood was drawn. Temperatures were taken, again.
Some recalled bleak, sometimes terrifying, last days in Wuhan.
Mr. Evans, a former quarterback at the University of Cincinnati, moved to Wuhan when he was recruited to play for the city’s American football team.
It had been a good season: His team had won the national championship in Shanghai on Jan. 8.
“I fell in love with Chinese culture,” he said, “and I got to be the face of American football in China.”
But when the coronavirus began spreading through Wuhan, Mr. Evans shut himself inside his apartment, stocked up with rice, noodles, eggs and disinfectant.
“I did exactly what every Chinese person did,” he said.
“I locked myself in. The city turned into a ghost town,” Mr. Evans said. But he felt isolated, he said, and his mother, back in the United States, was worried for his safety.
When he heard of a flight out of the country, he quickly filled out the online forms. An email from the United States Embassy in Beijing arrived, which read: “Space on this flight is extremely limited and we respectfully request that you not share details regarding the flight, including on social media.”
Mr. Evans learned that he was No. 171 on a flight that could accommodate about 200, he said. “I felt very lucky to be chosen out of all U.S. residents in Wuhan,” he said. Some Americans reported that they had tried to get a seat on the flight but were told there was no room.
Mr. McCoy, who lives in Shanghai, was in Wuhan working on a mall he is refashioning into a theme park when he got caught in the lockdown.
The atmosphere in the city was “just short of panic,” he recalled.
A former Marine who has run 12 marathons and stays in good shape, Mr. McCoy said he was convinced he had not contracted the virus. But he still took the outbreak seriously. He decided it was worth plunking down $1,100 for a one-way ticket to the United States.
When the American group left Wuhan, it had been made aware it would have to remain in an isolated location for at least 72 hours.
“This quarantine will occur for a minimum of 72 hours and may extend through 14 days or may be followed by conditional release with health monitoring,” said an email that he received before the flight. Mr. McCoy said that had not troubled most people. “Everyone was cool with that. We are trying to be patriots, trying to help,” he said. “We’re a captive audience here.”
On Thursday morning, their first full day back in the United States, the group downed breakfast burritos, juice and coffee. For lunch, they received a hearty taco salad with chicken.
An invitation slipped under the doors of the hotel rooms promised a “town hall discussion.” Federal health officials urged the group to remain on the base until receiving full medical clearance.
Now it was a matter of waiting.
Outside, there were refreshments, chips, cookies and toys. Scooters, footballs, soccer balls and Frisbees were available.
“People here have been really nice,” Mr. Evans said. “Everybody is in great spirits. Nobody is panicking or freaking out.”
There is no shaking hands or hugging, though, and most people were keeping on their masks.
Susan C. Beachy contributed research from New York.