Five members of Australia and Canada's badminton teams were among a number of guests who fell ill with food poisoning at a hotel in Derbyshire.
The Health Protection Agency (HPA) investigated when guests had stomach bugs after eating at the Mickleover Court Hotel, Derby, last week.
It said norovirus had been identified as the cause of the infection.
The three Australians have fully recovered but two Canadians had to miss a warm-up match on Saturday.
The three affected Australian badminton players were Ross Smith, Renuga Veeran and Glenn Warfe while Michelle Li and Alex Bruce were the ill Canadians.
The HPA said: "Norovirus has been identified as the cause of the infection and we are working with environmental health officers from South Derbyshire District Council to identify the source of the illness.
"Norovirus is the most common cause of infectious gastroenteritis (diarrhoea and vomiting) in England and Wales.
"People can suffer from norovirus at any time of the year, although activity increases in the winter months. It usually resolves in one or two days and there are no long-term effects."
The hotel, which briefly closed following the infection but has now reopened, is yet to comment.
