1. Department of Infectious Disease Epidemiology, School of Public Health, Imperial College Faculty of Medicine, St Mary's Campus, London W2 1PG, UK
2. Centre for Neglected Tropical Diseases, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
3. Department of Paediatrics and Molecular Virology and Microbiology, National School of Tropical Medicine, Baylor College of Medicine, Houston, TX, USA