Funding for this research was provided by:
Centers for Disease Control and Prevention (U2GGH000320)
Article History
Received: 3 February 2017
Accepted: 23 November 2017
First Online: 2 December 2017
Ethics approval
: The Health Research Ethics Committee of Stellenbosch University (S12/02/059) approved this study.
: Not applicable.
: The authors declare that they have no competing interests.
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