Chen Wang1, Simiao Chen2, Jiming Zhu3, Wenkai Li4. 1. Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China; Chinese Academy of Engineering, Beijing, China. Electronic address: wangchen@pumc.edu.cn. 2. Heidelberg Institute of Global Health, Faculty of Medicine and University Hospital, Heidelberg University, Heidelberg, Germany. 3. Research Centre for Public Health and Institute for Hospital Management, Tsinghua University, Beijing, China. 4. China Medical Board, Beijing, China.