The Trump administration said that it would deny entry to foreign nationals traveling from China to the U.S. and quarantine returning U.S. citizens to address the coronavirus outbreak.

Health and Human Services Secretary Alex Azar, chairman of President Trump's coronavirus task force, outlined the protective measures, which will go into effect Sunday, in announcing that he had declared a public health emergency over the virus.

Citizens returning to the U.S. who have traveled to Hubei province in China, the epicenter of the outbreak, in the past 14 days will now be quarantined for up to 14 days, Azar said. Returning citizens who've traveled to anywhere else in mainland China in the past 14 days will be subject to enhanced screening and "monitored self-quarantine" in their homes for 14 days.

Azar said that anyone who posed a risk of transmitting the virus would be denied entry to the U.S., meaning all foreign nationals who've been in China in the past 14 days, with the exception of immediate family members of U.S. citizens or permanent residents.

Azar called the measures "prudent, targeted, and temporary."

"This just helps us focus our efforts so that as we’re dealing with the unknowns … that we take appropriate measured prudential steps so that we can focus our resources because it’s the bread and butter of public health,” he said.

Warnings against travel to China have escalated quickly in the past week. The Centers for Disease Control and Prevention warned against “nonessential travel” to all of China on Tuesday . By Thursday, the State Department had issued a “Level 4: Do Not Travel” warning for travelers to avoid going to China.

Acting Deputy Secretary of Homeland Security Ken Cuccinelli said that starting Sunday at 5 p.m., all flights from China will enter through seven airports: John F. Kennedy in New York, Atlanta, Chicago, Honolulu airport, Los Angeles, San Francisco, and Seattle.

Cuccinelli said that "funneling" flights through specific airports will help to "focus the expertise of medical professionals who will be doing the [health] screening” at airports.

There is now a diagnostic test that health professionals at airports can use to screen travelers for the virus upon arrival, but members of the task force said the test's accuracy is lacking.

"We don't know the accuracy of this test," said Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases. "It isn't like it's a horrible test, but it's not a test that's absolute."

Only one patient in the U.S. was diagnosed with the virus after catching it from someone else, his wife. Dr. Robert Redfield, Director of the CDC, said that the particular case was an example of isolated human-to-human transmission, meaning that the risk of spreading the virus further throughout the U.S. is low.

“So that’s going to be important – to see if there’s broad and sustained human-to-human transmission,” Redfield said. “That’s going to be the major thing that we’re going to be looking at.”

Despite the two major updates Friday, Azar said the risk to the general American public is still low, and that people should not see the preventative measures as "extreme."

"I hope that people will see that their government is taking responsible steps to protect them," Azar said. "These are preventive steps. The risk is low in the United States."

The seventh case of coronavirus in the U.S. was confirmed Friday, the third in California. Nearly 10,000 people have been infected globally and at least 210 have died.

