Funding for this research was provided by:
State Education Ministry and the Science and Technology Basic and Advanced Research Projects in Chongqing (cstc2014jcyjA10069)
Received: 31 January 2020
Accepted: 18 March 2020
First Online: 24 March 2020
Ethics approval and consent to participate
: The project proposal was approved by the Institutional Review Board of Preventive Medicine College, Army Medical University (Third Military Medical University), Chongqing, China. All participants had completed written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.