1 Maternal and Child Health Division, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka 1000, Bangladesh. Electronic address: jena@icddrb.org.
2 School of Psychology, Bangor University, Bangor, UK.
3 Maternal and Child Health Division, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka 1000, Bangladesh.
4 University College London Great Ormond Street Institute of Child Health, London, UK.