1. Department of Internal Medicine, Faculty of Medicine, University of Khartoum, Khartoum, Sudan
2. Department of Internal Medicine, Faculty of Medicine, Nile Valley University, Khartoum, Sudan
3. Department of Environmental and Occupational Health, College of Public Health and Health Informatics, Umm Al-Qura University, Makkah, Saudi Arabia
4. Independent Scholar, Chesterfield, United Kingdom