LOS ANGELES — Americans evacuated from Hubei province in China arrived in California on government-arranged planes on Wednesday morning, and were greeted with applause by waiting medical personnel. They received health screenings, were warned to stay six feet away from the other families and were asked not to let children share toys.

Eventually, bleary-eyed from an 11-hour flight, they fell asleep in their new temporary homes on military bases.

The number of American evacuees from China under federal quarantine for the deadly coronavirus more than doubled on Wednesday with the arrival of two new planeloads of people. The new group of about 350, mostly American citizens, will be held at Travis Air Force Base in Fairfield, Calif., and at Marine Corps Air Station Miramar in San Diego for 14 days, believed to be the maximum time it takes a person to become ill after being exposed to the coronavirus.

At least one more government evacuation flight was expected later in the week to deliver passengers to bases in Nebraska and Texas; a flight last week carried nearly 200 Americans to another base in California. All told, more than 500 people were quarantined on three American bases by Wednesday evening, with more on the way.

Passengers who made the journey from China, where nearly 500 people have died in the outbreak, said they were relieved and exhausted, patiently enduring frequent checks of their temperature with little idea what they could expect under the highly unusual federal quarantine.

John McGory, 65, described a trip that spanned 37 hours from the time he left an apartment in Wuhan, the center of the outbreak, until he left the plane at Marine Corps Air Station Miramar.

“It was grueling,” said Mr. McGory, of Columbus, Ohio, who had been teaching in Wuhan. “It was very challenging.”

There were few signs of illness among those who have been evacuated from Wuhan so far.

The earlier group of evacuees from China — about 200 people who have been staying at a military base near Riverside, Calif., since last week — were told on Wednesday that all of their tests for coronavirus had come back negative, officials said. Still, they were expected to remain in quarantine for about another week, officials said, in case any symptoms emerged.

On the more recent evacuation flights on Wednesday, five people — three adults and two children — showed signs of cough or fever and were taken to hospitals for evaluation, according to the Centers for Disease Control and Prevention.

If life under quarantine was inconvenient or lonely, few were complaining. At least one person reportedly tried to leave the Riverside base before being stopped by officials, but evacuees said the group had settled into a routine.

Jarred Evans, 27, a football player from New York City who has been living in Wuhan for two years, said that staying at the base in Riverside for the full 14 days was “the most important thing we can do for the American people and the safety of our friends and family and community.”

Mr. Evans, who played for the Chinese National Football League champions, the Wuhan Berserkers, said that his group of evacuees had received daily updates about their health.

Another evacuee in Riverside described a genial atmosphere, despite the tense circumstances and lack of outside contact. There were Zumba classes, small business courses and a Super Bowl party on Sunday, complete with pizza, chicken wings and two big TV screens in a courtyard. A nonprofit organization, he said, had provided toys for children, as well as gourmet coffee and toiletries.

“Everybody’s O.K. here!,” Matthew McCoy, a theme-park designer who was on the first government-arranged flight out of Wuhan last week, said in an email. “We keep up with the news, other people’s work, and we all help each other as a group.”

Days in quarantine on military bases were expected as part of a strict protocol federal officials have put in place for the first time in about half a century to slow the spread of the outbreak.

Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases, part of the C.D.C., said she did not believe the evacuees posed a threat to the communities where they were being quarantined.

“Maybe we can’t catch every returning traveler, but if we can catch the majority of them, we will slow the spread of the virus in the United States,” she said. “We have a window of opportunity here.”

Family members who were awaiting the end of their relatives’ quarantines said they were understanding of the process, given the fears over coronavirus in the United States.

Samuel Roth, who works for a paper-goods manufacturer in Neenah, Wis., said his wife, Daisy, and their two daughters had been successfully evacuated from Wuhan to California.

He said they had been in Wuhan, Ms. Roth’s hometown, for what was supposed to be a happy family reunion with her parents.

But a quarantine now was welcome, Mr. Roth said: It would not go over well if Ms. Roth and daughters had been allowed to arrive in their community fresh off a flight from Wuhan, the sprawling center of the outbreak. In the United States, 12 cases of coronavirus have been identified, including a new case that was confirmed in Wisconsin on Wednesday.

“To be honest, just because I don’t really want the backlash of people thinking that my family is bringing the disease here,” he said. “I’ve not faced any discrimination or negative comments directly, but reading the paper and just seeing certain xenophobic behaviors online, I can imagine that there are people around me thinking, ‘I don’t really want the coronavirus in my community.’ And I don’t blame them.”

Also on the evacuation flights that arrived on Wednesday were two sisters and a niece of Guanettee Colebrooke, a Junior Reserve Officers’ Training Corps instructor in suburban Washington. Ms. Colebrooke said she was prepared to welcome them to her home in Virginia whenever they might be allowed to leave quarantine.

Her sisters, LaVana and Luanettee, were studying for advanced degrees in Wuhan, and had spent weeks holed up in their apartments in that city with bottled water and canned food.

“They feel so sad that there are so many people who are unable to be evacuated,” Ms. Colebrooke said. Her sisters made a simple calculation, she said: “They were like, ‘If we can get out of here, let’s get out.’”

Miriam Jordan reported from Los Angeles, and Julie Bosman from Chicago. Reporting was contributed by Thomas Fuller from San Francisco, Donald G. McNeil Jr. from New York, Dave Philipps from Colorado Springs, and Joe Purtell from Fairfield, Calif.