1 School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Sydney, 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, Australia. Electronic address: abrar.chughtai@unsw.edu.au.
3 School of Public Health and Community Medicine, Faculty of Medicine, University of New South Wales, Sydney, Australia. Electronic address: h.seale@unsw.edu.au.
4 University of the Witwatersrand Johannesburg, South Africa; Critical Care Charlotte Maxeke Johannesburg Academic Hospital, Johannesburg, South Africa. Electronic address: Guy.Richards@wits.ac.za.
5 Johns Hopkins University, Baltimore, USA; University of Technology, Sydney, Australia. Electronic address: pdavidson@jhu.edu.