1. Department of Population Health Research, Health Education and Research Organization , Buea , Cameroon
2. Division of Gastroenterology, Massachusetts General Hospital , Boston, Massachusetts , USA
3. Department of Research, Pan-African Organization for Health, Education and Research , Manchester, Missouri , USA
4. Division of Infectious Diseases, Massachusetts General Hospital , Boston, Massachusetts , USA
5. Medical Practice Evaluation Center, Massachusetts General Hospital , Boston, Massachusetts , USA
6. Department of Medicine, Harvard Medical School , Boston, Massachusetts , USA