Department of Respiration, Key Laboratory of Respiratory Disease Prevention and Control of Shanxi Department of Pulmonary and Critical Care Medicine, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China. School of Public Health, Sun Yat-sen University, Guangzhou 510080, Guangdong Province, China. Department of Epidemiology and Biostatistics, College for Public Health & Social Justice, Saint Louis University, 3545 Lafayette Avenue, Saint Louis, MO 63104, USA. Key Laboratory of Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China. Key Laboratory of Vaccine, Prevention and Control of Infectious Disease of Zhejiang Province, Zhejiang Provincial Center for Disease Control and Prevention, Hangzhou, Zhejiang, China. Department of Ideological and Political Education, School of Marxism, Capital Medical University, Beijing, China. Department of Standards and Evaluation, Beijing Municipal Health Commission Policy Research Center, Beijing Municipal health Commission Information Center, Beijing, China. School of Social Work, College for Public Health & Social Justice, Saint Louis University, Tegeler Hall, 3550 Lindell Boulevard, St. Louis, MO 631034, USA. Department of Epidemiology and Biostatistics, College of Public Health, Zhengzhou University, Zhengzhou, Henan, China. Department of Respiration, Key Laboratory of Respiratory Disease Prevention and Control of Shanxi Department of Pulmonary and Critical Care Medicine, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China. Electronic address: ykdzxr61@163.com. School of Public Health, Sun Yat-sen University, Guangzhou 510080, Guangdong Province, China. Electronic address: linhualiang@mail.sysu.edu.cn.