Received: 25 January 2018
Accepted: 30 August 2018
First Online: 10 September 2018
Ethics approval and consent to participate
: This observational study, data analysis and our manuscript were scientifically and ethically approved by the Centre for Disease Control and Prevention in Diqing. The approval was granted by Institutional Review Board at the Centre for Disease Control and Prevention in Diqing. Each participant with a unique code for individual differentiation provided a written informed consent before enrolment.
: Not applicable.
: The authors declare that they have no competing interests.
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