Funding for this research was provided by:
Yunnan Provincial Department of Health (NO. 2014NS354)
Received: 10 October 2019
Accepted: 22 November 2019
First Online: 21 December 2019
Ethical approval and consent to participate
: This retrospective study was consulted to the ethics committees of Yunnan Center for Disease Control and Prevention. Ethics approval was not available in this study because we did not include any data of patients’ personal information, including name, identity information, address, telephone number, etc. This study only reviewed of secondary aggregated data on county-level, therefore, waiver of written informed consent was taken and waived off ethical approval.
: Not applicable.
: The authors declare that they have no competing interests.