Funding for this research was provided by:
Chinese Academy of Medical Sciences (2017-I2M-B&R-17)
Received: 25 October 2019
Accepted: 5 November 2019
First Online: 21 November 2019
Ethics approval and consent to participate
: This study has been approved by the Institutional Review Board of Chinese Center for Disease Control and Prevention in July 2019 (approval number: 201918). Written informed consent forms will be obtained from all participants prior to the baseline survey. The results of the study will be published in peer-reviewed journals, and the findings will be presented at academic conferences or scientific meetings.
: Not applicable.
: The authors declare that they have no competing interests.