1. HIV and Hepatitis Research Unit, Department of Virology, Sefako Makgatho Health Sciences University, Pretoria 0208, South Africa
2. Division of Digestive Diseases, Department of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0595, USA
3. National Health Laboratory Service, Sefako Makgatho Health Sciences University, Pretoria 0208, South Africa