1. School of Public Health, Weifang Medical University, Weifang, China.
2. Weifang Center for Disease Control and Prevention, Shandong, China.
3. Yunnan Center for Disease Control and Prevention, Kunming, China.
4. Beijing Center for Disease Control and Prevention, Beijing, China.
5. Hunan Center for Disease Control and Prevention, Changsha, China.
6. Division of Risk Surveillance II, China National Center for Food Safety Risk Assessment, Beijing, China.