Doctor Xiao Yangbao puts on the mask before work at endoscopy center of Hunan Chest Hospital in Changsha, capital of central China's Hunan Province, Aug. 14, 2019. Xiao Yangbao, a 39-year-old doctor in endoscopy center of Hunan Chest Hospital, has been working on tuberculosis prevention and treatment for almost 8 years. As a doctor performing endoscopy operations, Xiao is in face of higher exposure risks for tuberculosis and higher operation requirements on preciseness and concentration. Xiao always feels gratified everytime his patients got well. So far he has completed nearly 30,000 operations. Doctors in the chest hospital have to wear masks during working hours, so they call themselves "Masked Guards". "As long as patients need me, I will always stick to my post here," said Xiao. (Xinhua/Xue Yuge)