1 Department of Respiratory and Critical Care Medicine, The Second Affiliated Hospital of Shandong First Medical University, Taian, China.
2 Key Laboratory of Aetiology and Epidemiology of Emerging Infectious Diseases in Universities of Shandong, Shandong First Medical University & Shandong Academy of Medical Sciences, Ji'nan 250117, China.
3 Key Laboratory of Aetiology and Epidemiology of Emerging Infectious Diseases in Universities of Shandong, Shandong First Medical University & Shandong Academy of Medical Sciences, Ji'nan 250117, China. Electronic address: zjzhang@sdfmu.edu.cn.