A woman waiting for an international traveler to arrive to LAX Tom Bradley International Terminal wears a medical mask for protection against the coronavirus outbreak on February 2, 2020 in Los Angeles, California.

The U.S. is accepting four new planes carrying Americans being evacuated from Wuhan, China, the epicenter of a new coronavirus outbreak that has infected more than 24,300 people across the world, the Centers for Disease Control and Prevention said Wednesday.

The Americans will be quarantined at four different military bases across the U.S.: Camp Ashland in Nebraska; Travis Air Force Base in California; Marine Corps Air Station Miramar in San Diego; and Lackland Air Force Base in Texas.

The four latest evacuation flights come after the first government-chartered flight from Wuhan landed at March Air Reserve Base in Riverside, California, last week. The flight's 195 passengers remain under quarantine at the base.

"This could be the beginning of what could be a long response," Dr. Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases, said on a conference call with reporters.

CDC officials announced the mandatory quarantine orders last week. It is the first time the U.S. government has issued federal quarantine orders in 50 years, officials said.

"While we recognize this is an unprecedented action, we are facing an unprecedented public health threat," Messonnier said last week.

CDC officials said there have been no new U.S. cases reported since confirming 11 infections earlier this week. Officials said 206 people have tested negative for the virus, while 76 possible cases are still awaiting results.

World Health Organization officials announced earlier Wednesday that the number of cases of the flu-like coronavirus surged in the last day, with more than 3,100 new patients confirmed in China. WHO Director-General Tedros Adhanom Ghebreyesus said at a news conference that the reported cases are "the most cases in a single day since the outbreak started" on Dec. 31.

Just 191 of the total cases are outside mainland China, and 80% of those cases are concentrated in Hubei province where the virus was first detected in the city of Wuhan, Tedros said. Of the cases outside of China, 31 spread through human-to-human contact, mostly from close friends or relatives who had recently been to China.

Infectious disease specialists and scientists say the virus may be more contagious than current data shows. Data on the virus is changing by the day, and some infectious disease specialists say it will take weeks before they can see just how contagious it is.

The respiratory illness is not yet considered a pandemic. According to WHO, a pandemic is "an epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people."