1 Department of Global Health and Development, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK. Electronic address: matthew.quaife@lshtm.ac.uk.
2 Population Health Sciences, University of Bristol, Bristol, UK.
3 Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK; Central Clinical School, Monash University, Melbourne, VIC, Australia.
4 Department of Global Health and Development, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.