Since the Lunar New Year holiday in China a month ago, many workers have been homebound, disrupting factories that assemble electronics or make automotive parts. Microsoft said this week that the virus had hampered production of its laptop and tablet computers, and it cut its sales forecast for the division that makes those products, scrapping a projection it had issued just a few weeks earlier.

The supply-chain problems have started to affect American homebuilders as well. A senior executive at Toll Brothers said the virus appeared to have delayed the supply of lighting parts.

At the same time, Chinese consumers are buying less. Apple said the closing of stores in China would depress sales of iPhones and other devices.

Mastercard cut its growth forecast in part because people are taking fewer international trips. Fear of the virus has prompted companies like Amazon and Nestlé to suspend international travel by some employees. That drop in demand, combined with their own concerns about the virus, has prompted United and other airlines in the United States and Europe to cancel flights to cities in China and elsewhere in Asia.