Wang Yu (1st R) takes a swab sample from a resident for COVID-19 test at a testing site of Longxi Community in Jiangning District of Nanjing, capital of east China's Jiangsu Province, July 24, 2021. A second round of COVID-19 nucleic acid test was launched Saturday night in Jiangning District of Nanjing. Wang Yu, a nurse from Dongshan Community Hospital in Jiangning District, was racing against time in epidemic battle on Saturday night. Wang, along with other medical workers and community workers, has been busy conducting nucleic acid tests for the residents until late night. (Xinhua/Li Bo)