1. Family Medicine Unit, Department of Community Medicine, College of Medicine University and Family Medicine Department, University College Hospital, Ibadan, Nigeria.
2. Geriatric Center, University College Hospital, Ibadan, Nigeria.
3. Division of Infectious Disease and Cancer Epidemiology, Department of Medicine and Preventive Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois.
4. Neurology Unit, Department of Medicine, College of Medicine, University of Ibadan, Ibadan, Nigeria.
5. Department of Virology, College of Medicine, University of Ibadan, Ibadan, Nigeria.