Seven thousand troops and civilians called up for round-the-clock border patrols. Four thousand medical workers rushed to the scene. Two Communist Party officials dismissed for failing to contain the outbreak.

In a locked-down border city abutting Myanmar, Chinese authorities are springing into crisis mode to stamp out a spike in coronavirus cases and seal the porous frontier amid fears that refugees could be streaming in to escape fighting in post-coup Myanmar, bringing with them covid-19 and instability.

The Ruili border zone, famous for its jade and emerald trade, is the busiest land crossing in southwest China and saw $11.4 billion in trade in 2019 with Muse, in Myanmar’s Shan state. The Ruili area also abuts Myanmar’s Kachin state, which has been riven by fighting between Kachin militias and the Myanmar military, known as the Tatmadaw.

Before the coronavirus outbreak, about 50,000 people crossed the border every day, including Myanmar people who work or have residency in China. Although the border closed last year, undocumented migrants have continued to cross the Ruili River and enter China, which is demarcated in some places by a simple railing from Myanmar, also known as Burma.

In the wake of the Feb. 1 coup, which triggered fighting among the military, protesters and ethnic militias throughout Myanmar, reports of undocumented crossings — and coronavirus infections — have ticked up in Ruili, a Chinese city of about 210,000.

Compounding the situation is the prevalence of anti-Chinese sentiment in Myanmar, where some protesters have been attacking ethnic Chinese-owned businesses.

In Ruili last week, thousands were drafted to form border patrols and erect barbed-wire fences. Chinese state media reports describing the extent of the all-hands mobilization say border guards — which include disabled farmers and teenage girls — assigned to overnight shifts have caught up to 10 people crossing into China a night.

“They’re mainly ethnic Chinese Burmese,” Tang Ming, the 35-year-old owner of an emerald shop, said by phone, describing the flow of migrants. “Although the Ruili government strengthened border management since last year, there is still a steady stream of people being smuggled over from Myanmar, whether due to the epidemic or to escape war.”

Some of Myanmar’s internal conflicts have lasted for decades and have sparked occasional surges of refugees into China. Since the February coup, ethnic militias including the Kachin Independence Army (KIA) have fought government forces near Muse, according to Chinese reports. The Irrawaddy, a Yangon-based news outlet, has reported that Shan armed groups have also been shelling each other in Shan state.

Duan, an ethnic Chinese Myanmar restaurant owner, said by telephone from a Ruili hotel that fighting was so close that it’s possible to hear gunfire from the free-trade zone in Ruili. He has not been able to return home to Myanmar for a year because of the border closure, Duan said. Nor does he want to go back given the turmoil — everyone is trying to get to China.

“When there’s fighting, everyone is terrified because people will die,” said Duan, who gave only his surname so he could discuss a sensitive subject. “If you can walk a few steps to stay alive, of course you’re going to walk over here” to China.

Chinese authorities have been scrambling to contain a parallel emergency: 131 coronavirus cases have been announced in Ruili as of Friday, a notable spike for a country that has practically stamped out domestic transmission. A Myanmar jade seller was one of the earliest cases last month, Chinese authorities said, sparking fears that cases were being imported from Myanmar.

Ruili officials launched a mass contact-tracing and quarantine drive and ordered the city into lockdown in recent days. Two local Communist Party officials were fired Thursday as case counts continued to climb.

Tang, the emerald shop owner, said Ruili’s streets and supermarkets suddenly emptied last week. Local authorities originally sought to carry out a mass vaccination campaign but paused it on Tuesday because they feared it would lead to more case clusters, he said, so they opted for a stay-at-home order instead.

China has a nearly 1,350-mile border with Myanmar. In 2017, fighting between the KIA and the military drove 20,000 refugees into southwest China’s Yunnan province, which includes Ruili, according to the United Nations refugee agency. In 2009, clashes in Shan state between the government and ethnic Chinese rebels forced 30,000 people into China.

Li reported from Seoul. Alicia Chen in Taipei contributed to this report.