More Americans were evacuated from the epicenter of the coronavirus outbreak in China late Thursday, as the number of cases worldwide surpassed 31,000.

Two chartered planes carrying about 300 Americans have left Wuhan, the U.S. State Department said Thursday night. Both flights will stop at Travis Air Force base in northern California, the Associated Press reported.

Anyone showing symptoms of illness will be quarantined there, while the planes continue on to military bases in San Antonio, Texas, and Omaha, Neb., the wire service said. But U.S. health officials said it is unlikely there will be any ill passengers on board either plane, the AP reported.

These are the fourth and fifth flights to evacuate Americans from China in the past week. About 540 Americans are already quarantined at two military bases in California, NBC News reported.

On Wednesday, two planes carrying 350 Americans landed at Travis Air Force base. Some of those passengers were then flown to Marine Corps Air Station Miramar near San Diego. Both groups were put under a 14-day quarantine, U.S. health officials said.

The first group of evacuees, who were flown out of Wuhan, China, a week ago, were moved off Travis Air Force Base in anticipation of the new arrivals, the AP reported.

That first group was told on Wednesday that they have all tested negative for coronavirus, health officials said. But they were to remain in quarantine for about another week, the New York Times reported.

On the evacuation flights that left China Wednesday, five people — three adults and two children — showed signs of cough or fever and were taken to hospitals for evaluation, according to the U.S. Centers for Disease Control and Prevention, the Times reported.

“CDC staff are there meeting the planes and assessing the health of each passenger,” Dr. Nancy Messonnier, director of the U.S. National Center for Immunization and Respiratory Diseases, said during a Wednesday media briefing. “The passengers will be screened, monitored and evaluated by medical and public health personnel, including before takeoff and during the flight.”

“The measures we are taking may not catch every single returning traveler with this novel coronavirus, given the nature of this virus and how it’s spreading,” Messonnier added. “But if we can catch the majority of them, that will slow the entry of this virus into the United States.”

Meanwhile, the U.S. Food and Drug Administration announced on Tuesday that it had fast-tracked a test for the virus in an effort to help speed screening efforts.

“Today, the test kits will start shipping to over 100 U.S. public health labs,” Messonnier said during the media briefing Wednesday. “Initially, 200 test kits will be distributed to U.S. domestic laboratories, and another 200 will be distributed to selected international laboratories. Each test kit can perform 700 to 800 patient samples.”

Twelve cases of coronavirus have been confirmed so far in the United States, with the latest case reported late Wednesday in Wisconsin, the AP reported.

But 11 Americans onboard a quarantined cruise ship in Japan have also tested positive for the virus, NBC News reported. So far, a total of 61 passengers on the Diamond Princess, docked in Yokohama, Japan, have confirmed illness.

Worldwide, there are now more than 31,000 cases of the new coronavirus, most of those in China. Two deaths outside China — one in the Philippines and one in Hong Kong — have also been reported, the Times said.

Since Sunday, the United States has begun to bar entry to any foreigners who have recently traveled to China.

Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, said the American actions were taken because there are “a lot of unknowns” surrounding the virus and its transmission path, the Times reported.

“The number of cases have steeply inclined with every day,” Fauci noted.

The temporary entry ban applies to foreign nationals, with the exception of relatives of citizens and permanent residents.

U.S. citizens who have recently traveled to the Hubei province of China, where Wuhan, the epicenter of the outbreak, is located, will be quarantined for up to 14 days, U.S. health officials said. U.S. citizens who have recently traveled to other parts of China will face health screenings and voluntary quarantines of up to 14 days.

The World Health Organization has already declared the new coronavirus outbreak an international public health emergency. Experts fear the outbreak could become a pandemic, where there are outbreaks on more than continent.

Meanwhile, Chinese officials said Thursday that the death toll in that country has hit 636, the Times reported. That’s nearly double the death total reported in mainland China in the 2003 SARS outbreak, which was 349.

China’s state broadcaster CCTV reported Wednesday that two newborns have been infected with the coronavirus in Wuhan, the epicenter of the outbreak, The youngest infant was diagnosed at just 30 hours old, CNN reported.

CCTV suggested that “there may be mother-infant transmission,” where the mother passes the virus on to the baby in utero, because the baby’s mother was also infected with the virus.

Chinese health officials have already said that the virus is spreading from person-to-person. And they also believe the virus can be spread by a person who is not showing symptoms of infection.

More information

The U.S. Centers for Disease Control and Prevention has more on the new coronavirus.