1 Centre for Clinical Microbiology, Division of Infection and Immunity, University College London, London WC1E 6BT, UK.
2 UCL Respiratory, Division of Medicine, University College London, London, UK; Royal Free London National Health Service Foundation Trust, London, UK.
3 Centre for Clinical Microbiology, Division of Infection and Immunity, University College London, London WC1E 6BT, UK; National Institute for Health Research Biomedical Research Centre, UCL Hospitals NHS Foundation Trust, London, UK. Electronic address: a.zumla@ucl.ac.uk.