Text and Data Mining valid from 2019-01-30
Received: 29 June 2018
Accepted: 14 January 2019
First Online: 30 January 2019
Ethics approval and consent to participate
: Written informed consent forms were obtained from all subjects.Medical Research Coordinating Committee of Yulin CDC approved the study.
: Not applicable.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.