Photo taken on Oct. 20, 2021 shows residents taking nucleic acid tests at a testing site in Chengguan District of Lanzhou, northwest China's Gansu Province. Northwest China's Gansu Province reported four new locally transmitted confirmed COVID-19 cases between 11 p.m. Tuesday and 11 a.m. Wednesday. Local authorities have stepped up prevention and control measures to curb the spread of the coronavirus. (Xinhua/Ma Xiping)
