On Aug. 3, a day after officials reported 11 cases of Covid-19 in Sanya, a city of more than one million in Hainan, Ms. Chan was identified by the authorities as at risk because she had been in the area that day. She was told to quarantine right away for a three-day monitoring period and to undergo two coronavirus tests.

After her isolation period was over and her tests negative, Ms. Chan, a freelance videographer, was told that she was not allowed to come to the airport because she had traveled to Sanya. It took 10 more days, 10 canceled flights and more than a dozen negative test results before she was permitted to leave the island and fly back to Shanghai, where she lives.

With China’s borders still shut, some people have turned to domestic travel to find relief from the aggressive testing, mass quarantines and widespread lockdowns that have become common in cities across the country. But China’s commitment to ensuring no Covid-19 cases in a population of 1.4 billion people has meant that even domestic tourists risk traveling to the wrong place at the wrong time and getting stuck there.

“It’s like playing Russian roulette with travel,” Ms. Chan said. “So much of it is out of your hands and out of your control.”