1 Department of Paediatrics and Child Health, Red Cross Children's Hospital, Cape Town, South Africa; SA MRC Unit on Child and Adolescent Health, University of Cape Town, Cape Town, South Africa. Electronic address: heather.zar@uct.ac.za.
2 Division of Medical Microbiology, Department of Pathology, University of Cape Town, Cape Town, South Africa; National Health Laboratory Service of South Africa, Cape Town, South Africa.