Funding for this research was provided by:
National Natural Science Foundation of China (30972517, 81773372, 81373058, 81573104)
Text and Data Mining valid from 2019-01-07
Received: 15 March 2018
Accepted: 17 December 2018
First Online: 7 January 2019
Ethics approval and consent to participate
: The Ethics Committee of Fourth Military Medical University (Grant No.: 2015018) approved this study. The study has got the written consent to participate from the participants. Data analyzed in this study were previously gathered and had been de-identified. Data is got from Xi’an CDC disease surveillance system which is not public, and this study got the written permission of use these data from Xi’an CDC.
: Not Applicable.
: The authors declare that they have no competing interests.
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