1. Noguchi Memorial Institute for Medical Research, University of Ghana, Legon,1 and
2. Enteric and Respiratory Virus Laboratory, Virus Reference Division, Central Public Health Laboratory, Colindale, London NW9 5HT,2
3. Clinical Microbiology and Public Health Laboratory, Addenbrooke's Hospital, Cambridge CB2 2QW,3 and
4. Navrongo Health Research Centre, Navrongo, Upper East Region,4 Ghana, and
5. London School of Tropical Medicine and Hygiene, London,5 United Kingdom