Funding for this research was provided by:
Sichuan Province Science and Technology Support Program (2020YFS0015)
Received: 18 March 2020
Accepted: 22 June 2020
First Online: 12 August 2020
Ethics approval and consent to participate
: The ethics committee of Sichuan Center for Disease Control and Prevention, Chengdu, China approved this research. NO. SCCDCCIRB 2020–005.
: Written informed consent was obtained from all persons described in this paper.
: The authors declare that they have no competing interests.