Funding for this research was provided by:
Received: 13 July 2018
Accepted: 7 June 2019
First Online: 8 July 2019
Ethics approval and consent to participate
: The study was approved by the Human Research Ethics Committee (Medical) (HREC) at the University of the Witwatersrand (Ref: 160412). Administrative approvals were also received from the Gauteng Provincial Department of Health and the City of Johannesburg District Management. Eligible participants were requested to provide written informed consent prior to enrolment in the study.
: Not applicable.
: The authors declare that they have no competing interests.