1. MRC/MEDUNSA Diarrhoeal Pathogens Research Unit, PO Box 173, Medunsa 0204, Pretoria, South Africa1
2. Department of Virology, Camelia Botnar Laboratories, Great Ormond Street Hospital, London, UK2
3. Department of Medical Virology, Institute of Pathology, University of Pretoria, Pretoria, South Africa3