TRAVIS AIR FORCE BASE (CBS SF) — Four passengers from Friday’s flight evacuating American citizens out of China have been hospitalized with possible symptoms of the coronavirus, a Centers for Disease Control and Prevention spokesman said.

CDC spokesman Jason McDonald said the four patients had been taken to a local hospital in Northern California and were in isolation while tests were being run to determine the source of their fever. They join a child from an earlier flight that also has been hospitalized.

UPDATE: For The Latest Coverage On The Coronavirus Outbreak

“Anyone who may appear to be symptomatic will be transported to an area hospital and tested to try to determine what’s causing the fever,” he said.

CDC Dr. Henry Walke said the four passengers joined a child from an earlier flight who was also showing signs of the illness.

“Four of the patients arrived this morning and one arrived another day,” he said. “They will stay in isolation until we can determine they don’t have the coronavirus or figure out if they have a different disease.”

For the second time this week, a flight of evacuees arrived at Travis early Friday with the bulk of the passengers continuing on to Lackland Air Force Base in San Antonio, Texas.

For strictly logistical reasons, McDonald said, 53 of the 201 Friday arrivals remained on the Northern California base and joined the 170 evacuees already under 14-day quarantine there.

Health officials screened passengers on the flight for any sign of the coronavirus as the plane was being refueled at Travis before departing for its final destination.

Travis is one of six military bases designated by the Pentagon as landing spots for the flights from China.

A plane carrying evacuees from the Coronavirus outbreak in Wuhan, China landed at Travis Air Force Base in Fairfield on February 7, 2020. (CBS)

A plane carrying evacuees from the Coronavirus outbreak in Wuhan, China landed at Travis Air Force Base in Fairfield on February 7, 2020. (CBS)

Meanwhile, about 170 passengers from a flight earlier this week remain quarantined inside a converted hotel on the Travis base. They were in their third day of a 14-day stay required by health officials.

The evacuees range in age from under 2 to over 65. Most are American citizens who either traveled or lived in Hubei province, where Wuhan is the provincial capital.

“While this is an unprecedented action, we are facing an unprecedented health threat,” Walke said at the start of the quarantine.” We are utilizing all of our tools in our tool box.”

KPIX 5 was able to speak with a family that was part of the group being quarantined. Daisy Roth had been traveling in China visiting family with her two young daughters, ages 5 and 10 months old.

“Exhaustion is really the overriding emotion,” said Roth.

Her husband Sam Roth is now waiting for his family to come home to Wisconsin, but he knows they will have to remain at Travis for at least two weeks.

“This whole trip, I’ve been worried about their immune system. I’m going to let them rest,” he said.

Because of the high risk of exposure, the quarantined group will be screened daily. One child on the flight had a fever and was taken away to be evaluated at an area hospital.

“A parent did accompany the child. We don’t want to separate the child from mother,” said Dr. Walke.

The news about the ill child raised serious concerns for Sam Roth.

“That’s my worst fear. It’s the first I’m hearing about it,” he said. “I hope that child gets well and my children don’t get infected.”

The quarantined travelers will receive health evaluations to check for symptoms of the virus and have their temperature taken twice a day. They are not restricted to their rooms, but each family unit was told to stay 6 feet (nearly 2 meters) away from other families, along with other precautions.

“We don’t want kids to share toys between the families,” Walke said.

It is not known if anyone in the group is carrying the virus, as it can go undetected for two weeks. 14 days is the longest incubation period. This is the first time in 50 years the CDC has issued a quarantine.

“They are happy and relieved to be back in the United States,” Dr, Christopher Braden of the Centers for Disease Control, said of the evacuees who arrived in at another base in San Diego earlier this week.

The Chinese government announced Friday that the death toll in mainland China has risen to at least 636. The outbreak has now infected more than 31,400 people worldwide.

The new virus is a member of the coronavirus family that’s a close cousin to the SARS and MERS viruses that have caused outbreaks in the past.

© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.

Comments