Funding for this research was provided by:
Nanjing Medical Science and technique Development Foundation (QRX11038)
Jiangsu Province Association of Science and Technology (JSKXKT2018)
Received: 5 August 2018
Accepted: 4 September 2019
First Online: 7 October 2019
Ethics approval and consent to participate
: The Academic and Ethical Committee of Nanjing Municipal Center for Disease Control and Prevention approved this study. Written informed consent was obtained from each participant before our survey.
: Not applicable.
: Prof. Fei Xu is an Associate Editor of BMC Public Health. No other competing interests exist.