1 Burnet Institute, Melbourne, VIC 3004, Australia; Department of Epidemiology and Preventive Medicine, Monash University, Clayton, VIC 3008, Australia; Department of Infectious Diseases, The Alfred Hospital and Monash University, Melbourne, VIC 3004, Australia. Electronic address: margaret.hellard@burnet.edu.au.
2 Burnet Institute, Melbourne, VIC 3004, Australia; Department of Epidemiology and Preventive Medicine, Monash University, Clayton, VIC 3008, Australia.
3 Burnet Institute, Melbourne, VIC 3004, Australia; Department of Medicine, University of Melbourne, Parkville, VIC 3010.