Funding for this research was provided by:
zhejiang medical and health science and technology project (2015KYA189)
Received: 16 January 2018
Accepted: 16 April 2018
First Online: 2 May 2018
Ethics approval and consent to participate
: The study was approved by the ethics committee of Hangzhou City Center for Disease Control and Prevention.
: All authors have reviewed and approved the manuscript for publication.
: All authors declare that they have no competing interests.
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