1. Department of Respiratory Medicine, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, P.R. China
2. Department of Internal Medicine, Xiamen Haicang Hospital, Xiamen, Fujian 361026, P.R. China
3. Department of Hospital Infection Management, Fujian Medical University Union Hospital, Fuzhou, Fujian 350001, P.R. China