1. Department of Epidemiology and Biostatistics, School of Public Health, Wannan Medical College, Wuhu, Anhui 241002, P.R. China
2. Department of Rheumatology, Affiliated Yijishan Hospital of Wannan Medical College, Wuhu, Anhui 241001, P.R. China
3. Hospital Infection Control Office, Affiliated Yijishan Hospital of Wannan Medical College, Wuhu, Anhui 241001, P.R. China