1. Mahidol University—Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, 420/6 Rajvithi Road, Bangkok 10400, Thailand
2. Centre for Tropical Medicine, University of Oxford, Churchill Hospital, Oxford OX3 7LJ, England
3. Armed Forces Research Institute of Medical Sciences, 315/6 Rajvithi Road, Bangkok 10400, Thailand
4. Department of Military Medicine, Royal Centre for Defence Medicine, Vincent Drive, Birmingham B15 2SQ, England
5. Department of Medicine, University of Kelaniya, P.O. Box 6, Thalagolla Road, Ragama, Sri Lanka
6. Clinical Research Group, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, England