A medical worker collects a swab sample of a student for nucleic acid testing at a primary school in Lu'an, east China's Anhui Province, May 17, 2021. Lu'an started to conduct a second round of nucleic acid testing for people in the city's main districts and in key areas from Monday to Wednesday, according to the commission. Authorities conducted the first round of testing from May 14 to 16 in the city proper, with more than 1 million samples collected. (Xinhua/Zhou Mu)
