1. MRC/UCT Medical Imaging Research Unit, Department of Human Biology, Faculty of Health Sciences; University of Cape Town; Observatory Cape Town South Africa
2. African Institute for Mathematical Sciences; Western Cape South Africa
3. Children's Infectious Diseases Clinical Research Unit, Department of Pediatrics and Child Health; Stellenbosch University and Tygerberg Hospital; Cape Town South Africa
4. Massachusetts General Hospital, Athinoula A. Martinos Center, Harvard Medical School; Charlestown MA USA