1. Lung Health Group, Malawi Liverpool Wellcome Trust Clinical Research Programme, Blantyre, Malawi, Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, UK
2. Department of Paediatrics and Child Health, University of KwaZulu Natal, Durban, South Africa
3. Department of Medicine, University of Malawi College of Medicine, University of Malawi, Blantyre, Malawi
4. Department of Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, UK