Secretary of Health and Human Services Alex Azar on Friday declared a public health emergency over the new coronavirus.
Starting Sunday at 5 p.m. ET, all passengers on flights to the United States who have been in Hubei province in China in the last 14 days will be subject to up to 14 days of quarantine. The city of Wuhan, the epicenter of the outbreak, is located in Hubei.
Any U.S. citizen who has been in the rest of mainland China will be actively screened at one of seven airports for risk and evidence of symptoms. If no symptoms are detected, the individuals will be allowed to complete their travel home and will be monitored by local health departments in isolation at home.
The seven airports are in New York, San Francisco, Seattle, Honolulu, Los Angeles, Chicago and Atlanta.
President Donald Trump's administration also announced that it will not allow anyone who has been in China recently to enter the U.S.
"The president has signed a presidential proclamation," Azar said during a news conference, "temporarily suspending the entry into the United States of foreign nationals who pose a risk of transmitting the 2019 novel coronavirus."
The proclamation applies to anyone other than immediate family of U.S. citizens.
The announcement comes just hours after the Centers for Disease Control and Prevention announced all 195 American evacuees who flew from Wuhan to the U.S. this week are under federal quarantine for 14 days.
The last time the CDC issued a quarantine was in the 1960s, for smallpox.
"We are preparing as if this were the next pandemic, but we are hopeful still that this is not and will not be the case," Dr. Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, said during a call earlier Friday with journalists.
Full coverage of the coronavirus outbreak
Overnight, the case count in China reached nearly 10,000 people, a 26 percent increase from the previous day, the CDC said.
Seven cases of the coronavirus had been confirmed in the U.S. on Friday afternoon: one each in Arizona and Washington, and two in Illinois, a married couple.
Three patients have been diagnosed in different parts of California; Santa Clara County, Los Angeles County and Orange County.
The CDC reported Friday it had received 241 samples for testing. Seven have come back positive, and 114 were negative. The rest are pending.
Follow NBC HEALTH on Twitter & Facebook.