1. London Northwest Healthcare Trust, Harrow, United Kingdom.
2. Victorian Cytology Services Registries, East Melbourne, Australia.
3. Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Carlton, Australia.
4. Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
5. International Centre for Diarrheal Disease Research, Bangladesh (icddr, b), Dhaka, Bangladesh.