1 School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia. Electronic address: r.macintyre@unsw.edu.au.
2 School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Sydney, NSW, Australia.
3 University of the Witwatersrand Johannesburg, Johannesburg, South Africa; Critical Care Charlotte Maxeke Johannesburg Academic Hospital, Johannesburg, South Africa.
4 Johns Hopkins University, Baltimore, ML, USA; University of Technology, Sydney, Australia.