1. Department of Epidemiology, School of Public Health, Southern Medical University, Guangzhou, China.
2. Department of Infectious Disease, Nanfang Hospital, Guangzhou, China.
3. Maternal and Child Health Hospital of Longgang, Shenzhen, China.
4. Center for Disease Control and Prevention of Shunde, Foshan, China.
5. Center for Disease Control and Prevention of Shenzhen, Shenzhen, China.
6. Department of Nosocomial Infection Administration, Zhujiang Hospital, Southern Medical University, Guangzhou, China.