Funding for this research was provided by:
National Major Science and Technology Projects of China (BE2017749)
Jiangsu Provincial natural science foundation (BK20151595)
Jiangsu Provincial Medical Youth Talent (QNRC2016542)
Key Medical Discipline of Epidemiology (ZDXK A2016008)
National Science and Technology Infrastructure Program (2018ZX10714-002)
Received: 1 October 2019
Accepted: 27 February 2020
First Online: 14 March 2020
Ethics approval and consent to participate
: This study was approved by the Ethics Committee at Jiangsu Provincial Center for Disease Control and Prevention, China. As the incidence was statistical summary data, it was not necessary to obtain informed consent.
: Not applicable.
: The authors declare that they have no competing interests.