MSRA-1166

An epidemic of diarrhoea and vomiting has broken out on one of the elderly care wards. The catering suppliers assure you that their food is unlikely to be responsible because they follow the strictest hygiene procedures. A total of 15 elderly patients on the ward have become unwell with a sudden onset of diarrhoea and vomiting. Those infected earlier have recovered with rehydration therapy after about 48 hours. Examination of faeces by electron microscopy has revealed circular virus particles with radiating spokes.
Which virus is most likely to be responsible for this outbreak?