Funding for this research was provided by:
National Natural Science Foundation of China (71702131, 71373146)
China Scholarship Council (201706220244)
Text and Data Mining valid from 2019-01-08
Received: 28 March 2018
Accepted: 20 December 2018
First Online: 8 January 2019
Ethics approval and consent to participate
: The project was approved by the Medical Ethics Committee at the Shandong University School of Medicine (Grant No. 201001052). Written informed consent was obtained from all participants prior to research.Participants were informed that they could refuse to answer any question. The questionnaire did not ask about infection status, and no biological samples were collected.
: Not applicable.
: None of the authors has any conflicts of interest.
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