ACUTE gastroenteritis is one of the most common causes of illness in children, calves and piglets, and causes severe economic loss in domestic animals. Although some outbreaks of gastroenteritis are associated with bacterial pathogens, particularly Escherichia coli, no known pathogens had been isolated from a significant proportion of outbreaks until recently, when viruses with a distinctive morphology and antigenic similarity were found associated with diarrhoea in piglets, calves and children1,2. These viruses are major pathogens and it has also been shown that viruses isolated from man are infectious for the pig3. Initially, these viruses were described as reovirus-like4 but subsequently the names rotavirus5 and duovirus6 were proposed. They are morphologically and antigenically distinct from both the reoviruses and orbiviruses5,7 and also differ from them in some of their physicochemical properties8.