A medical worker collects a swab sample from a resident of the Ronghui residential compound in Daxing's Tiangongyuan subdistrict, Beijing, capital of China, Jan. 29, 2021. Ronghui residential compound conducted a new round of nucleic acid tests on Friday. The COVID-19 risk classification of the residential compound was upgraded to high-risk on Jan. 20. (Xinhua/Sun Ruibo)

A medical worker collects a swab sample from a resident of the Ronghui residential compound in Daxing's Tiangongyuan subdistrict, Beijing, capital of China, Jan. 29, 2021. Ronghui residential compound conducted a new round of nucleic acid tests on Friday. The COVID-19 risk classification of the residential compound was upgraded to high-risk on Jan. 20. (Xinhua/Sun Ruibo)

Residents of the Ronghui residential compound wait in line for COVID-19 tests in Daxing's Tiangongyuan subdistrict, Beijing, capital of China, Jan. 29, 2021. Ronghui residential compound conducted a new round of nucleic acid tests on Friday. The COVID-19 risk classification of the residential compound was upgraded to high-risk on Jan. 20. (Xinhua/Sun Ruibo)

A medical worker checks the personal information of residents of the Ronghui residential compound in Daxing's Tiangongyuan subdistrict, Beijing, capital of China, Jan. 29, 2021. Ronghui residential compound conducted a new round of nucleic acid tests on Friday. The COVID-19 risk classification of the residential compound was upgraded to high-risk on Jan. 20. (Xinhua/Sun Ruibo)