1 Mason Unit, Médecins Sans Frontières, London EC4A 1AB, UK; TB Centre, London School of Hygiene & Tropical Medicine, London, UK. Electronic address: bern.nyangwa@london.msf.org.
2 Mason Unit, Médecins Sans Frontières, London EC4A 1AB, UK.
3 TB Centre, London School of Hygiene & Tropical Medicine, London, UK.
4 Medical Research Council Clinical Trials Unit, University College London, London, UK.