Received: 17 July 2018
Accepted: 31 October 2018
First Online: 19 November 2018
Ethics approval and consent to participate
: The study was approved by the University of Cape Town, Faculty of Health Sciences Human Research Ethics Committee and by the Western Cape Health Research Committee.
: 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.