Medical Microbiology and Immunology Department, Biomedical Division, School of Medicine, Mekelle University, PO. Box: 1871, Mekelle, Ethiopia. muheab2008@yahoo.com. Department of Family Medicine, CAPHRI School for Public Health and Primary Care, Maastricht University, Maastricht, The Netherlands. School of Public Health, College of Health Sciences, Mekelle University, Mekelle, Ethiopia. Department of Surgery, School of Medicine, Alcala University, Madrid, Spain.