1. Department of Emergency Medicine, University of Rochester, 601 Elmwood Avenue, P.O. Box 655, Rochester, NY 14642, USA
2. Desmond Tutu HIV Centre, Institute of Infectious Diseases & Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town, South Africa
3. Institute of Infectious Diseases & Molecular Medicine and Division of Medical Virology, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory, Cape Town, South Africa
4. National Health Laboratory Service, Groote Schuur Hospital, Cape Town, South Africa