A volunteer guides people to take COVID-19 nucleic acid tests in Nanjing, east China's Jiangsu Province, Aug. 5, 2021. Nanjing launched a fifth round of nucleic acid testing in some areas of the city on Thursday. (Xinhua/Ji Chunpeng)

Residents wait to take COVID-19 nucleic acid tests in Nanjing, east China's Jiangsu Province, Aug. 5, 2021. Nanjing launched a fifth round of nucleic acid testing in some areas of the city on Thursday. (Xinhua/Ji Chunpeng)

A volunteer guides people to take COVID-19 nucleic acid tests in Nanjing, east China's Jiangsu Province, Aug. 5, 2021. Nanjing launched a fifth round of nucleic acid testing in some areas of the city on Thursday. (Xinhua/Ji Chunpeng)

A medical worker prepares to take a swab sample from a woman for COVID-19 nucleic acid test in Nanjing, east China's Jiangsu Province, Aug. 5, 2021. Nanjing launched a fifth round of nucleic acid testing in some areas of the city on Thursday. (Xinhua/Ji Chunpeng)

A medical worker takes a swab sample from a woman for COVID-19 nucleic acid test in Nanjing, east China's Jiangsu Province, Aug. 5, 2021. Nanjing launched a fifth round of nucleic acid testing in some areas of the city on Thursday. (Xinhua/Ji Chunpeng)

A medical worker takes a swab sample from a woman for COVID-19 nucleic acid test in Nanjing, east China's Jiangsu Province, Aug. 5, 2021. Nanjing launched a fifth round of nucleic acid testing in some areas of the city on Thursday. (Xinhua/Ji Chunpeng)

Residents wait to take COVID-19 nucleic acid tests in Nanjing, east China's Jiangsu Province, Aug. 5, 2021. Nanjing launched a fifth round of nucleic acid testing in some areas of the city on Thursday. (Xinhua/Ji Chunpeng)

A medical worker takes a swab sample from a resident for COVID-19 nucleic acid test in Nanjing, east China's Jiangsu Province, Aug. 5, 2021. Nanjing launched a fifth round of nucleic acid testing in some areas of the city on Thursday. (Xinhua/Ji Chunpeng)

来源：Xinhua