1. Department of Family Medicine and Public Health Medicine, School of Medicine, University of Botswana, Private Bag UB, Gaborone 0022, Botswana
2. Department of Public Health, School of Health Care Sciences, Sefako Makgatho Health Sciences University, Pretoria 0208, South Africa
3. Faculty of Health Sciences, University of Limpopo, Polokwane 0700, South Africa