Funding for this research was provided by:
Science and Technology Major Project of Qinghai Province (No. 2016-SF-A5)
Received: 10 January 2020
Accepted: 1 June 2020
First Online: 15 June 2020
Ethics approval and consent to participate
: The study was approved by the Ethics Committee of Qinghai Institute of Endemic Disease Control and Prevention, and all participants signed informed consent forms.
: Not applicable.
: The authors declare that they have no competing interests.