The Department of Homeland Security has issued supplemental guidance on travel to the United States for individuals who have been in China. U.S. citizens who have been in China’s Hubei province within 14 days of their return to the United States will be subject to up to 14 days of mandatory quarantine upon arrival to ensure they are provided proper medical care and health screening. U.S. citizens who have been in other areas of mainland China within 14 days of their return to the United States will undergo proactive entry health screening and up to 14 days of self-quarantine with health monitoring to ensure they have not contracted the virus and do not pose a public health risk. Generally, foreign nationals (other than immediate family of U.S. citizens, permanent residents, and flight crew) who have traveled in China within 14 days of their arrival, will be denied entry into the United States.
More information is located here: https://www.dhs.gov/news/2020/02/02/dhs-issues-supplemental-instructions-inbound-flights-individuals-who-have-been-china