Text and Data Mining valid from 2019-06-04
Received: 21 February 2019
Accepted: 21 May 2019
First Online: 4 June 2019
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: All procedures performed in the study involving human participants were in accordance with the ethical standards of the Korea Centers for Disease Control and Prevention Institutional Review Board and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants included in the study.