Funding for this research was provided by:
Sichuan Province Science and Technology Support Program (2017JY0302)
Received: 12 February 2020
Accepted: 8 October 2020
First Online: 19 October 2020
Ethics approval and consent to participate
: This study was reviewed and approved by the ethics committees of Sichuan Center for Disease Prevention and Control. All participants signed written informed consents prior to sample donations.
: Not applicable.
: The authors declare no competing financial interests exist.