1. Assistant Clinical Professor, University of California, Division of Pulmonary & Critical Care Medicine, San Francisco General Hospital, San Francisco, CA, USA and, Francis J. Curry National Tuberculosis Center, 3180 18th Street, Suite 102, San Francisco, CA 94110-2028, USA.
2. World Health Organization, UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases, 1211 Geneva 27, Switzerland.
3. McGill University, Dept. of Epidemiology, Biostatistics & Occupational Health, Montréal, Canada and, Respiratory Epidemiology & Clinical Research Unit, Montréal Chest Institute 1020 Pine Avenue West Montreal, Canada.