Forsake, a footwear company based in Boston, has most of its supply chain and production facility in Zhongshan in southeastern China. The company received its spring orders before the annual holiday closing and is stocked through July. After that, said Sam Barstow, the president and chief operating officer, who knows?

“We don’t really know what we’re planning for,” Mr. Barstow said.

Tim Cook, Apple’s chief executive, said on an earnings call this week that many of its suppliers’ factories in China would remain closed until Feb. 10.

Apple had closed one retail store in China, and said traffic into its stores across China had decreased in recent days. Apple is frequently “deep cleaning” its stores and regularly checking the temperature of its employees there, Mr. Cook said.

The airlines are also braced for prolonged turmoil. American said all of its flights between the United States and mainland China were being suspended immediately, through March 27.

United and Delta said their flights on those routes would be suspended by next Thursday. United said it expected to resume operations on March 28, while Delta said its suspension would last through April 30. The three airlines accounted for more than a third of all travel between China and the United States in 2018.

In 2018, more than 8.5 million passengers traveled between the United States and China, according to data from the United States Transportation Department. Most flew on a handful of Chinese airlines, none of which immediately responded to requests for comment Friday on any plans to halt or modify service.

The coronavirus has already sickened more people than the outbreak of the SARS virus did in the eight-month outbreak of 2002 and 2003.