A staff member works at the polymerase chain reaction (PCR) laboratory in the disease prevention and control center of Changxing County in Huzhou City, east China's Zhejiang Province, April 21, 2020. The laboratory has been operating around the clock to conduct testings for COVID-19 to support the resumption of production and reopening of schools in the city. (Photo by Tan Yunfeng/Xinhua)