A staff member disinfects a classroom at a middle school in Lanzhou, northwest China's Gansu Province, Oct. 20, 2021. 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/Chen Bin)
