Text and Data Mining valid from 2017-02-01
Received: 12 December 2016
Accepted: 20 February 2017
First Online: 27 February 2017
Compliance with Ethics Guidelines
: The authors declare that they have no conflicts of interest. The study was approved by the Ethics Committees of the Centers for Disease Control and Prevention of Hubei Province. Written consents were obtained from all participants involved in the study.