University of Oxford - Respiratory Medicine Unit, University of Oxford, University of Oxford, University of Oxford, University of Oxford - Nuffield Department of Clinical Medicine, University of Oxford, University of Oxford, University of Oxford, Cardiff University - University Hospital Llandough, University of Oxford - Respiratory Medicine Unit, St. George's Hospital Medical School - Emergency Department, East Lancashire Hospitals NHS Trust, Oxford University Hospitals NHS Foundation Trust - Emergency Department, Independent, King's College Hospital, Royal Berkshire NHS Foundation Trust, University College Hospital, Cardiff and Vale University Health Board - Department of Infectious Diseases, University of Oxford - Oxford University Hospitals, University of Oxford - National Institute for Health Research (NIHR) Oxford Biomedical Research Centre (BRC), University of Oxford and University of Oxford - Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS)