Funding for this research was provided by:
National Natural Science Foundation of China (81573230)
Ministry of Science and Technology of the People's Republic of China (2015DFA31580)
the Science Technology Department of Jilin Province (20150101130JC)
the Scientific Research Foundation of the Health Bureau of Jilin Province, China (2011Z116)
Text and Data Mining valid from 2019-03-15
Received: 5 June 2018
Accepted: 25 February 2019
First Online: 15 March 2019
Ethics approval and consent to participate
: All participants provided written informed consent prior to participating in the survey. This study was approved by the ethics committee of Jilin Center for Disease Control and Prevention.
: Publication consent was obtained from all individual participants included in the study.
: The authors declare that they have no competing interests.
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