A citizen receives test at a nucleic acid testing point in Yangzhou, east China's Jiangsu Province, Aug. 7, 2021. Yangzhou launched the 4th round of nucleic acid testing in its main districts on Saturday. (Xinhua/Li Bo)

A citizen receives test at a nucleic acid testing point in Yangzhou, east China's Jiangsu Province, Aug. 7, 2021. Yangzhou launched the 4th round of nucleic acid testing in its main districts on Saturday. (Xinhua/Li Bo)

Citizens queue to receive test at a nucleic acid testing point in Yangzhou, east China's Jiangsu Province, Aug. 7, 2021. Yangzhou launched the 4th round of nucleic acid testing in its main districts on Saturday. (Xinhua/Li Bo)

A volunteer works at a nucleic acid testing point in Yangzhou, east China's Jiangsu Province, Aug. 7, 2021. Yangzhou launched the 4th round of nucleic acid testing in its main districts on Saturday. (Xinhua/Li Bo)

A police officer escorts the nucleic acid testing samples in Yangzhou, east China's Jiangsu Province, Aug. 7, 2021. Yangzhou launched the 4th round of nucleic acid testing in its main districts on Saturday. (Xinhua/Li Bo)

A citizen receives test at a nucleic acid testing point in Yangzhou, east China's Jiangsu Province, Aug. 7, 2021. Yangzhou launched the 4th round of nucleic acid testing in its main districts on Saturday. (Xinhua/Li Bo)