1. Department of Respiratory and Critical Care Medicine, Sichuan Academy of Medical Sciences & Sichuan Province People’s Hospital, Chengdu, P.R. China
2. Department of Aged Infectious Diseases, Sichuan Academy of Medical Sciences & Sichuan Province People’s Hospital, Chengdu, P.R. China
3. Department of Respiratory Diseases, Sichuan West China Hospital Geriatric Center-Fifth People’s Hospital of Sichuan Province, Chengdu, P.R. China
4. Department of Respiratory Diseases, Ziyang City People’s Hospital, Ziyang, P.R. China