Liu, Qin
Hou, Yaping
Yang, Liu
Zhao, Min
Li, Shengxu
Xi, Bo
Article History
Received: 29 September 2018
Accepted: 16 January 2019
First Online: 1 February 2019
Compliance with Ethical Standards
:
: The authors have no conflicts of interest relevant to this article to disclose.
: The study has been approved by institutional committee of Centers for Disease Control and Prevention.
: Informed consent was obtained from both the participants and their parents or guardians.