1. Department of Epidemiology and Biostatistics, College of Public Health and Medical Sciences, Jimma University, P.O. Box 24414, Jimma, Ethiopia
2. Department of Public Health, College of Health Sciences, Haramaya University, P.O. Box 1014, Harar, Ethiopia
3. Addis Continental Institute of Public Health, P.O. Box 1014, Addis Ababa, Ethiopia