On Wednesday, the U.S. Department of State announced that it would be "suspending routine visa services in most countries worldwide" in response to the Wuhan flu pandemic. As a result of this suspension, the affected embassies and consulates are cancelling routine appointments for both immigrant and non-immigrant visas.
Overnight, the U.S. Embassy in South Korea in its own statement said the suspension would affect both immigrant and non-immigrant visa services at embassies in countries with a U.S. State Department travel advisory level of 2, 3, or 4.
As of Wednesday that includes around 100 countries for which warnings have been issued, according to the U.S. State Department website. Reasons for those warnings range from outbreaks of the new coronavirus to war to crime.
Countries that are under levels two to four travel advisories range from Mexico (crime) to Italy (Wuhan flu) to India (crime and terrorism) to China (Wuhan flu) to Israel (travel restrictions and quarantine procedures in response to the Wuhan flu).
This suspension will almost definitely limit the number of foreign nationals entering the United States for the foreseeable future on not just visitor visas (note, however, that 39 countries are under the Visa Waiver Program, which is not affected by this suspension) but also work- and business-related visas. That said, with much of the United States shut down, and many Americans temporarily seeking employment, there should be more than sufficient labor supply to meet the demand.