1. Environment and Health Research Unit; South African Medical Research Council; Pretoria South Africa
2. Department of Geography, Geoinformatics and Meteorology; University of Pretoria; Pretoria South Africa
3. National Centre for Epidemiology and Population Health; Research School of Population Health; Australian National University; Canberra ACT Australia
4. Centre for Ophthalmology and Visual Sciences; University of Western Australia; Perth WA Australia
5. School of Medicine and Public Health; The University of Newcastle; Callaghan NSW Australia
6. Environment and Health Research Unit; South African Medical Research Council; Johannesburg South Africa
7. Department of General Medicine and Infectious Diseases; Canberra Hospital; Canberra ACT Australia
8. Department of Community Medicine; School of Public Health; University of the Witwatersrand; Johannesburg South Africa
9. Environmental Health Department; Faculty of Health Sciences; University of Johannesburg; Johannesburg South Africa