Received: 9 May 2019
Accepted: 23 September 2019
First Online: 17 October 2019
Ethics approval and consent to participate
: This study was approved by the National Ethics Committee for Health Research (NECHR) of the Ministry of Health, Cambodia (No. 420 NECHR). A written informed consent was obtained from each participant.
: Not applicable.
: The authors declare that they have no competing interests.