Received: 18 November 2017
Accepted: 26 April 2018
First Online: 22 May 2018
Ethics approval and consent to participate
: This study was conducted under compliance with the Declaration of Helsinki and were approved by the Human Ethics Committee of Yantai Infectious Disease Hospital and the Human Ethics Committee of Yantai Yuhuangding hospital.
: The authors declare that they have no competing interests.
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