On January 31, the Trump administration announced the following sweeping new travel restrictions:
Responding to the Coronavirus Situation, United States Restricts Travel From China
U.S. Health and Human Services Secretary Azar announced a ban on foreign nationals traveling from China and quarantines for U.S. citizens coming from China. The restrictions went into effect at 5:00 p.m. (EST) on Sunday, February 2.
• "Foreign nationals, other than immediate family of U.S. citizens and permanent residents, who have traveled in China within the last 14 days will be denied entry into the United States for this time," per a presidential proclamation under INA 212(f), signed by President Trump on January 31.
• Any U.S. citizen returning to the United States who has been in Hubei province in the 14 days prior to their entry to the United States will be subject to up to 14 days of mandatory quarantine to ensure they have been provided proper medical care and health screening
• Any U.S. citizen returning to the United States who has been anywhere else in mainland China in the 14 days prior to their entry to the United States will undergo "proactive entry health screening at a select number of ports of entry," and up to 14 days of "monitored self-quarantine" to ensure they have not contracted the virus and do not pose a public health risk.
Furthermore, on January 30, the World Health Organization declared that the spread of the virus is a Public Health Emergency of International Concern while, the U.S. State Department issued a Level 4 “do not travel” advisory for China.
Please note, the US Embassy Consulates in China are temporarily closed February 3-7 in accordance with Chinese government guidance.  As such, when they re-open, they will likely be backlogged so visa processing could see substantial delays.
In a January 31, 2020, Presidential Proclamation, the Trump administration expanded its travel ban to place visa and entry restrictions on travelers from six additional countries, including Eritrea, Kyrgyzstan, Myanmar, Nigeria, Sudan, and Tanzania.
The expanded ban will become effective at 12:01 a.m. (EST) on February 21, 2020. The ban contains restrictions on certain (not all) immigrant visa petitions being processed abroad at U.S. Embassies but does not impact nonimmigrants. Therefore, it will not impact applications for Adjustment of Status to Permanent Resident from within the U.S., acquisition of nonimmigrant visas like B-1/B-2 tourist, F-1 student, J-1 exchange visitor, H-1B worker, etc., or of admission to the United States in those categories. However, visitors in these may still be subject to extra scrutiny, as we have seen in the case of Iranian citizens most recently.