Designated hospitals in the Chinese city at the center of a coronavirus outbreak started taking only severe or critical patients, as more Chinese cities imposed restrictions on movement to help contain the fast-spreading pathogen that has killed nearly 500 people. Meanwhile, two major U.S. airlines, United Airlines Holdings Inc. and American Airlines Group Inc. suspended flights to Hong Kong until Feb. 20, citing a lack of demand, as the number of confirmed cases on the Chinese mainland grew beyond 24,000. Both airlines and…