1. Division of Infection and Immunity; Walter and Eliza Hall Institute; 3052 Melbourne Vic. Australia
2. Department of Medical Biology; University of Melbourne; 3052 Melbourne Vic. Australia
3. Papua New Guinea Institute of Medical Research; Goroka Papua New Guinea
4. Centre for Population Health; Burnet Institute; 3004 Melbourne Vic. Australia
5. Barcelona Centre for International Health Research (CRESIB); Barcelona Spain