1. University of North Carolina at Chapel Hill School of Medicine, Campus Box 7570, 130 Farm Mason Road, Chapel Hill, NC 27599, United States of America (USA).
2. Department of Medical Statistics, University of East Anglia, Norwich, England.
3. Zambian Ministry of Health, Lusaka, Zambia.
4. Centre for Infectious Disease Research in Zambia, Lusaka, Zambia.
5. Vanderbilt University School of Medicine, Nashville, USA.