1. School of Public Health, Guangdong Pharmaceutical University, Guangzhou 510200, China
2. Guangdong Provincial Institute of Public Health, Guangdong Provincial Center for Disease Control and Prevention, Guangzhou 511430, China
3. The Second Division Center for Disease Control and Prevention of Xinjiang Production and Construction Corps, Tiemenguan 841007, China
4. Guangdong Provincial Center for Disease Control and Prevention, Guangzhou 511430, China