General Motors, Ford and other U.S. companies have started restricting employee travel to Wuhan, China, as an outbreak of a flu-like coronavirus that has killed at least 17 people spreads throughout Asia.

The Centers for Disease Control and Prevention and Homeland Security started screening passengers flying to major U.S. airports from China for the disease over the weekend. The World Health Organization convened an emergency meeting in Geneva on Wednesday to assess the severity of the illness and issue recommendations to control the outbreak.

Fears that the coronavirus could disrupt travel and commerce and slow economic growth sent a chill through global risk markets, hitting Asian stocks hard, depressing copper and oil prices, and sending investors into safe havens, such as U.S. Treasurys and German bunds.

Business leaders at the World Economic Forum in Davos, Switzerland, privately expressed concerns this week about the virus, according to people with direct knowledge of the matter. Some even raised the issue directly with President Donald Trump at a private breakfast Wednesday morning, according to an executive who attended the meeting.

The Association of Flight Attendants, which represents about 50,000 cabin crew members at 20 airlines including United, said Tuesday it was contacting airlines to put in place precautions for crew members, while the Air Line Pilots Association distributed information from U.S. and international health officials on the virus.

General Motors has placed a temporary restriction on travel to the Chinese city where the outbreak emerged over the holidays, "out of an abundance of caution," the company said in a statement. "Employees are also reminded to take necessary protection measures suggested by medical authorities."

Ford Motor "has suspended all business travel to Wuhan, specifically, and is monitoring the situation very closely," a company spokesman said, adding that the Detroit automaker hasn't suspended travel to other parts of China.

Fiat Chrysler hasn't imposed any travel restrictions "at this time," but it's advising employees to travel to China only for "essential business." It's also implemented a travel advisory for all people who need to get around in the region, a company spokesman said.

Norwegian Cruise Line is beginning to screen passengers departing from Chinese ports, according to a company spokesperson. The Miami-based cruise line won't let anyone who's traveling from Wuhan, China, or who has been in the city over the last 30 days to board. It's also denying boarding for guests with a body temperature of 100.4 degrees Fahrenheit or more.

This story is developing. Please check back for updates.

— CNBC's Leslie Josephs, Brian Schwartz and Michael Wayland and Reuters contributed to this article.