China is testing all 5 million residents of a city in Xinjiang after one person tested positive for COVID-19

• China started testing 4.75 million residents in Kashgar, Xinjiang, for the coronavirus on Sunday, state media reported.
• The mass testing came after a 17-year-old girl who worked in a garment factory in the city tested positive for COVID-19 on Saturday, Xinhua news agency reported.
• One hundred and thirty-seven people, who were asymptomatic, later tested positive on Sunday, according to state-run broadcaster CGTN.
• Kashgar is the largest city in Xinjiang, one of the most surveilled parts of China. The government has been monitoring and persecuting Uighur Muslims in the region for years.
• Testing entire cities in a short time frame has become a hallmark of China's response to the latter stages of its pandemic.

China started testing all 4.75 million residents of a major city for COVID-19 on Sunday after identifying one positive test the day before, state media reported.

Health authorities announced the plan to mass-test the city of Kashgar after a 17-year-old female garment worker tested positive for the virus during a routine screening on Saturday, the state-run Xinhua news agency reported. It's not clear how she was infected, Xinhua said.

More than 2.84 million people have been tested already, Reuters reported early Monday morning, adding that the remaining tests would be completed by Tuesday.

By the end of Sunday 137 people, who were all asymptomatic, had tested positive, state-run broadcaster CGTN reported. Xinhua said that all the new cases are linked to another garment factory where the teenager's parents worked, according to Reuters.

The reported new infections in Kashgar mark the largest flare-up seen anywhere in China since April 1, according to Reuters.

Kashgar lies in the Xinjiang region of western China, which is one of the most closely-surveilled parts of the country.

Since 2016, China has been trying to eradicate Uighur Muslim culture in the region, and has detained at least one million Uighurs in a series of camps masquerading as reeducation centers there.

Kashgar is at the center of that surveillance network, as the The New York Times detailed in 2019. The mass coronavirus testing in the city may give the government even more data on its residents.

Testing entire cities in a short time frame has become a hallmark of China's response to the latter stages of its pandemic.

Authorities in Wuhan, where the outbreak began in December 2019, said on May 25 that they had tested 9 million residents in ten days following the discovery of a handful of new cases, the first to be found in the city for more than 30 days.

And in early October, authorities in Qingdao, a city on China's east coast, tested 11 million people after finding 12 new locally transmitted cases. Testing there began on October 12 and was completed on October 16.

The flare-up in Kashgar is the first since that seen in Qingdao.

China, which drew international criticism for not doing enough to curb the outbreak during the first weeks of the outbreak, has since successfully stopped its outbreak from consuming the country.

Experts have praised China for its speedy testing processes, stringent and comprehensive lockdowns, and well-developed contact tracing techniques.