1. School of Geography and the Environment, University of Oxford, Oxford OX1 3QY, UK
2. Imperial College Healthcare NHS Trust, Charing Cross Hospital, London, W6 8RF
3. London School of Hygiene and Tropical Medicine, Faculty of Public Health and Policy, London WC1E 7HT, UK
4. Public Health Scotland, Gyle Square, 1 S Gyle Cres, Edinburgh EH12 9EB, UK