1. Department of Physiological Sciences, School of Medicine, University of Zambia, Ridgeway Campus, P.O. Box 50110, 10101 Lusaka, Zambia
2. Department of Public Health, Section for Epidemiology and Biostatistics, School of Medicine, University of Zambia, Ridgeway Campus, P.O. Box 50110, 10101 Lusaka, Zambia