1. Inspection Department, People's Hospital of Rizhao, Rizhao, Shandong 276800, P.R. China
2. Rizhao Disease Prevention and Control Center, People's Hospital of Rizhao, Rizhao, Shandong 276800, P.R. China
3. Nursing Department, People's Hospital of Rizhao, Rizhao, Shandong 276800, P.R. China