1 Department of Biostatistics, University of Florida, Gainesville, FL, USA.
2 Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland; Centre for Infectious Disease Epidemiology and Research, University of Cape Town, Cape Town, South Africa.
3 Faculty of Epidemiology & Population Health, London School of Hygiene & Tropical Medicine, London, UK.
4 World Health Organization, 1211 Geneva 27, Switzerland. Electronic address: henaorestrepoa@who.int.