1. School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC 3004, Australia
2. Department of Epidemiology and Biostatistics, Institute of Public Health, College of Medicine and Health Sciences, University of Gondar, Gondar 196, Ethiopia
3. Department of Respiratory Medicine, Alfred Health, Melbourne, VIC 3004, Australia
4. Faculty of Medicine, Nursing and Health Sciences, Central Clinical School, Monash University, Melbourne, VIC 3004, Australia