Funding for this research was provided by:
National Research Foundation (TTK170430229217)
Received: 18 August 2019
Accepted: 6 November 2019
First Online: 5 December 2019
Ethics approval and consent to participate
: The study was approved by the University of Witwatersrand Human Research Ethics Committee (M1704100). All participants signed written informed consent.
: The authors declare that they have no competing interests.