Funding for this research was provided by:
Health Commission of Yunnan Province (2016NS118)
Received: 29 September 2018
Accepted: 28 December 2018
First Online: 15 January 2019
Ethics approval and consent to participate
: This study was approved by the Ethics Committee of Kunming Medical University. Written informed consent was obtained from children’s guardians before the study.
: Not applicable.
: The authors declare that they have no competing interests.
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