M Wang1, J Peng2, J Hui1, D Hou1, W Li1, J Yang3. 1. Department of Disease Control and Prevention, Naval Medical Center of PLA, Naval Medical University, Shanghai 200052, China. 2. Department of Quality Management, Guangdong Second Provincial General Hospital (Pazhou Campus), Guangzhou, Guangdong 510317, China. 3. Medical Care Center, Naval Medical Center of PLA, Naval Medical University, Shanghai, 200052, China.