1 Department of Biological and Environmental Sciences, Walter Sisulu University, Mthatha 5117, South Africa. Electronic address: bnkehchungag@wsu.ac.za.
2 Faculty of Medicine, Universidade Eduardo Mondlane, Maputo, Mozambique; Cape Heart Institute, Department of Medicine, University of Cape Town, Cape Town, South Africa; Institute for Health Research, University of Notre Dame, Fremantle, WA, Australia.