Funding for this research was provided by:
National Health Commission and the Ministry of Science and Technology of the People’s Republic of China (2012ZX10001-007)
Text and Data Mining valid from 2019-12-01
Received: 12 June 2019
Accepted: 14 November 2019
First Online: 3 December 2019
Ethics approval and consent to participate
: The study was approved by the Institutional Review Board of the National Center for AIDS/STD Control and Prevention of the Chinese Center for Disease Control and Prevention. A signed, informed consent form was obtained from all participants (The approval number is X120717225).
: Not applicable.
: The authors declare that they have no competing interest.