*Corresponding authors:
Runyu Yuan, Ph.D., cecilia_yry@hotmail.com, Guangdong Provincial
Institute of Public Health, Guangdong Provincial Center for Disease
Control and Prevention, Guangzhou, China.
Jiufeng Sun, Ph.D., sunjiuf@163.com, Guangdong Provincial Institute of
Public Health, Guangdong Provincial Center for Disease Control and
Prevention, Guangzhou, China.
Baisheng Li, Ph.D., libsn@126.com, Guangdong Provincial Center for
Disease Control and Prevention, Guangzhou, China.