MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, United Kingdom.|Department of Biology, University of Florida, Gainesville, Florida, United States of America.|Department of Epidemiology, Johns Hopkins University, Baltimore, Maryland, United States of America.|Department of Epidemiology, Johns Hopkins University, Baltimore, Maryland, United States of America.|Centre for Health Informatics Computing and Statistics, Lancaster Medical School, Lancaster University, Lancaster, United Kingdom.|MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, United Kingdom.