Students wait in lines for nucleic acid tests at the Xihua University in Pidu District of Chengdu, southwest China''s Sichuan Province, Dec. 11, 2020. Southwest China''s Chengdu launched a nucleic acid testing drive Friday, offering free tests to all residents in the city''s Pidu District, where several new COVID-19 cases have emerged since earlier this week. The district''s COVID-19 prevention and control headquarters said the drive started at 6 p.m., with testing expenses covered by the district government. (Xinhua/Shen Bohan)