1 Division of Epidemiology and Public Health, School of Medicine, University of Nottingham, Nottingham NG5 1PB, UK.
2 Department of Respiratory Sciences, University of Leicester, Leicester, UK; Department of Infection and HIV Medicine, University Hospitals Leicester NHS Trust, Leicester, UK.
3 International Organization for Migration, Geneva, Switzerland.
4 Division of Epidemiology and Public Health, School of Medicine, University of Nottingham, Nottingham NG5 1PB, UK. Electronic address: laura.nellums@nottingham.ac.uk.