1. Department of Epidemiology and Biostatistics, School of Public Health, Anhui Medical University, Hefei, People's Republic of China.
2. Anhui Provincial Laboratory of Population Health & Major Disease Screening and Diagnosis, Anhui Medical University, Hefei, People's Republic of China.
3. Department of Hospital Infection Management, Yijishan Hospital of Wannan Medical College, Wuhu, People's Republic of China.
4. Department of Human Resources, the Second People's Hospital of Wuhu City, Wuhu, People's Republic of China.