1. Department of Epidemiology, School of Public Health, Cheeloo College of Medicine, Shandong University, Jinan, China.
2. Shandong Center for Disease Control and Prevention, Jinan, China.
3. Shandong Provincial Qianfoshan Hospital, Jinan, China.
4. Guangzhou Center for Disease Control and Prevention, Guangzhou, China.
5. Zengcheng District Center for Disease Control and Prevention, Guangzhou, China.