1 Department of Health, Johannesburg, South Africa.
2 School of Population and Public Health (SPPH), University of British Columbia (UBC), 430-2206 East Mall, Vancouver, BC, V6T 1Z3, Canada.
3 Centre of African Studies, University of Edinburgh, Edinburgh, UK.
4 School of Population and Public Health (SPPH), University of British Columbia (UBC), 430-2206 East Mall, Vancouver, BC, V6T 1Z3, Canada. jerry.spiegel@ubc.ca.