A growing number of volunteers is stepping up. Wang Xiaoyu reports from Ruili, Yunnan, with Li Yingqing in Kunming.

Having viewed many posts about Ruili, Yunnan province, on Douyin, a short-video app, Qin Yao saw the city as a wonderland of exotic culture based around the Dai and Jingpo ethnic groups, immersive carnivals and festivals.

"I heard that people wandering around the city might accidentally find themselves stepping into a village in neighboring Myanmar," the 21-year-old said of the posts she saw on the app, which is known in the West as TikTok.

"It sounded fascinating, so I always wanted to visit the city."

In the event, she visited Ruili earlier than she had planned, but not as a tourist.

Right after she graduated from a vocational college for health studies in late June, Qin arrived in the city as a healthcare worker on the front line of the COVID-19 battle.

Ruili, hemmed in by Myanmar on three sides, shares a long border that has few natural barriers. For decades, residents on both sides have been in close contact, with about 50,000 border crossings a day before the outbreak.

Amid the raging pandemic, the city's proximity to Myanmar has pitted it in a tough and protracted battle against the novel coronavirus and COVID-19.