A medical worker collects a throat swab sample to test for COVID-19 at Ruili People's Hospital in Yunnan province on Sept 14, 2020. (YANG XUEMEI / CHINA DAILY)

Ruili, a city in Yunnan province that lies on the border with Myanmar, will begin free mass nucleic acid testing of all residents after reporting two cases of COVID-19 on Sunday — both in illegal immigrants who arrived in the city recently — the local government said on Monday night.

From 10 pm on Monday, no people will be allowed in or out of Ruili's urban area for a week except under special circumstances, and all residents will be placed under home-based isolation, Xie Dapeng, the city's mayor, said at a news conference.

Those who had left Ruili since Saturday should report to community authorities at their destinations and take nucleic acid tests, he said.

The city has also ramped up border controls, locking down all border villages, prohibiting any cross-border movement and heightening precautions against illegal immigration

The two imported cases are both Myanmar citizens, one of them a 32-year-old female surnamed Yang and the other a 16-year-old nanny hired by Yang.

They crossed the border from Myanmar to China illegally on Sept 3, along with three of Yang's children and another nanny. They lived together in an apartment in a residential community. On Sunday the pair were confirmed to have contracted the novel coronavirus.

A total of 190 close contacts were tracked down by 4 pm on Monday and 98 of them who had taken the tests showed negative results.

The two-block residential community where they lived has been locked down since 7:30 pm on Saturday, and tests on 1,185 of its residents returned negative results. There are 1,560 residents in total.

The city has also ramped up border controls, locking down all border villages, prohibiting any cross-border movement and heightening precautions against illegal immigration.

According to a notice released by the city's epidemic control command center on Sunday, the number of residents in bordering villages and their movement should be clearly recorded. Any cross-border visits to family members or friends are now prohibited.

The local government has also stepped up efforts to crack down on illegal crossings and to persuade illegal immigrants to return. Those who violate the rule will be handled by local public security, according to the notice.

A citywide screening campaign that targets illegal immigrants in particular will be rolled out to identify hidden risks of the virus' spread and strengthening awareness about disease control measures.

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Meetings will be reduced and large gatherings, including the city's live broadcasts and trading activities for jade and jewelry, will be halted, according to the notice. This apart, all weddings will be delayed, and funerals will be held in a simple manner.

Mask-wearing will be mandatory in all public spaces, including supermarkets, hotels and workplaces. A variety of virus control policies, such as taking temperatures, conducting disinfections and presenting health codes will also be strengthened.

The local government will also enhance communication with Myanmar, transmitting information on the conditions of the two cases and urging the country to step up border controls.

The China-Myanmar border in Ruili stretches nearly 170 kilometers, and residents on both sides have been interacting closely for a long time, according to Yang Bianqiang, vice-mayor of Ruili.

The border actually runs through the village of Yinjing.

During a video conference with health and foreign affairs officials of Myanmar on Monday, the Chinese embassy in Myanmar said both sides should join efforts to stem the spread of the virus as new infections imported from Myanmar were recently detected in arrivals by air and by road.

More efforts will be devoted to testing flight passengers before their arrival in China, cracking down on illegal border crossings and stepping up information sharing. China will also provide aid to Myanmar.

Myanmar officials said that it will ask local governments in border regions to enhance cooperation with Yunnan and strive to reduce the risk of the virus's spread to the minimum.

As the virus continues to rage worldwide, the Ruili government has taken steps to crack down on illegal immigrants, including shutting down illegal ports, confiscating boats and conducting regular patrols.

However, Yang said the detection of imported cases in the city had exposed weaknesses in its border control work.

He added that it will send protective equipment and financial support to Myanmar if requested and help the country set up more checkpoints in border villages.

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On Monday, no new confirmed or asymptomatic cases were reported in Ruili.

However, Kunming, the capital of Yunnan, registered a new confirmed case on Monday in a man who arrived in the city on Sept 4 on a flight from Indonesia.

He was diagnosed as an asymptomatic carrier of the virus on Sept 7.