1. Wellcome Trust Clinical Research Unit, Centre for Tropical Diseases,1 and
2. Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford University, John Radcliffe Hospital, Oxford,2 and
3. Dong Thap Provincial Hospital, Cao Lanh, Dong Thap,3Vietnam,
4. Centre for Tropical Diseases,4 Ho Chi Minh City, and
5. Department of Histopathology, Imperial College School of Medicine, Hammersmith Campus, London, W12 0NN,5 United Kingdom