SHANGHAI—To celebrate Christmas one year, Jing Sun trekked to the North Pole to see reindeer. For another holiday, the Shenzhen native flew to Marrakesh, and she was recently in Cleveland for work. Los Angeles, New York and Barcelona were on her spring itinerary, while her maiden Australia voyage was penciled in.

Suddenly, the 29-year-old is grounded in Beijing.

Fearing...