1. Department of Medical Microbiology, Ahmadu Bello University, Zaria, Nigeria.
2. Nigeria Field Epidemiology and Laboratory Training Programme, Abuja, Nigeria.
3. Nigeria Center for Disease Control, Abuja, Nigeria.
4. Epidemiology Division, Federal Ministry of Health, Abuja, Nigeria.
5. Immunology Unit, Department of Medicine, Ahmadu Bello University Teaching Hospital, Zaria, Nigeria.