1. Population Council, One Dag Hammarskjold Plaza, New York, New York 10017
2. Columbia University Medical Center, 622 W. 168th St., PH16-80, New York, New York 10032
3. Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory 7925, Cape Town, South Africa
4. Academic Medical Center, Center for Poverty-Related Communicable Diseases, University of Amsterdam, Meibergdreef 9 T0-120, 1105 AZ Amsterdam, The Netherlands
5. Infectious Disease Epidemiology Unit, School of Public Health, and Faculty of Health Sciences, University of Cape Town, Anzio Road, Observatory 7925, Cape Town, South Africa
6. Shropshire and Staffordshire Health Protection Unit, Health Protection Agency, Mellor House, Corporation Street, Stafford, Staffordshire ST16 3SR, United Kingdom
7. and National Health Laboratory Service, Groote Schuur Hospital, Observatory 7925, Cape Town, South Africa