1. School of Public Health, Moi University, P.O. Box 4606-30100, Eldoret, Kenya
2. School of Public Health, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200, Nairobi, Kenya
3. Kenya Medical Research Institute, P.O. Box 54840 00200, Mbagathi Road, Nairobi, Kenya