1 Infectious Diseases and Respiratory Medicine, The Royal London Hospital, Barts Health NHS Trust, Whitechapel Rd., Whitechapel, London, E1 1BB, UK. Electronic address: nidaahmed@nhs.net.
2 GKT School of Medical Education, Guy's Campus, Great Maze Pond, London, SE1 1UL, UK.
3 Lewisham and Greenwich NHS Trust, Lewisham High St., Lewisham, London, SE13 6LH, UK.