Because of a growing coronavirus outbreak that originated in Wuhan, China, the US will temporarily bar foreign nationals who have been in China within the past 14 days, the Trump administration announced on Friday.

US citizens and permanent residents who have recently traveled to China’s Hubei province will be screened on arrival and may be subject to quarantine.

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The Trump administration announced on Friday that it would temporarily bar foreigners from entering the US if they have been to China within the past 14 days.

The action will effectively prevent any foreign national who has been to China within the past two weeks from entering the country, with exceptions made for immediate family of American citizens and permanent residents.

US citizens returning home who have been in China’s Hubei province within the prior 14 days will be quarantined for up to two weeks, Secretary of Health and Human Services Alex Azar said at a press briefing on Friday.

Those who recently traveled to other parts of China will be subject to “proactive entry health screening” and up to two weeks of “monitored self-quarantine to ensure they’ve not contracted the virus and do not pose a public health risk,” Azar added.

The rules are scheduled to take effect at 5 p.m. ET on Sunday.

“The American public can be assured the full weight of the US government is working to safeguard the health and safety of the American people,” Azar said.

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The US will also funnel all flights from China to just seven airports in New York, Atlanta, Seattle, Honolulu, Los Angeles, San Francisco, and Chicago.

US airlines have suspended service to China amid plummeting demand because of the coronavirus. However, Chinese airlines are continuing to fly to the US, and connections through other countries in Asia remain an option for travelers between American and Chinese cities.

It was not immediately clear whether Chinese airlines would continue flying to the US given the barring of foreigners who had been in China recently.

The city of Wuhan, China, where the coronavirus outbreak originated, and the larger Hubei province have been quarantined by Chinese officials since January 23.

Travel between China and the US has dropped significantly since the Hubei quarantine began.

“Since the Chinese have locked down the Hubei province, travel from China to the US as of yesterday had dropped by close to 12%,” Ken Cuccinelli, the acting director of the US Citizenship and Immigration Service, said during the briefing. “Travel from US to China had dropped by well more than 50%.”

US health officials began screening arriving passengers at several airports earlier this month.

Chinese health officials say the incubation period for the virus ranges from one to 14 days, during which time carriers can be infectious even if they don’t show symptoms. The Centers for Disease Control and Prevention has a test for the virus, but the agency’s director, Robert Redfield, said it was not fully reliable.

“We’ve seen people who had a detectable virus, then they didn’t have a detectable virus, and then three days later they had a detectable virus,” Redfield said. “We don’t know the natural history of how this virus is secreted.”

The US reported its first case of the novel coronavirus on January 21, when a man in his 30s was confirmed sick in Snohomish County, Washington. Since then, six other cases have been reported. The latest, a man in the San Francisco Bay Area’s Santa Clara County (home to Silicon Valley), was announced on Friday.

Two other California cases were reported in Los Angeles and Orange County. Two patients are also being treated in Chicago. A woman in her 60s was confirmed sick there after she traveled to Wuhan in December, and the CDC confirmed on Thursday that the woman’s husband was also ill, which marked the first case of human-to-human transmission of the virus in the US.

The other US case was in Maricopa County, Arizona, which includes Phoenix.

Redfield said he expected more cases to appear in the US despite the travel ban.

“We are going to see additional cases in this country,” he said. “In the six cases we defined, a number of them came in asymptomatic.”

Earlier on Friday, the CDC issued a mandatory quarantine order to nearly 200 Americans who were evacuated from China earlier this week. It was the first CDC quarantine in more than 50 years.

The coronavirus has sickened nearly 10,000 people and killed at least 213. It has spread to at least 22 countries.